TL;DR: Weapon Focus does suck, because by the time you have gotten your build’s mission-critical feats (which will never include Weapon Focus unless you need it as a prerequisite), its static +1 bonus is too tiny to make much difference.
Monster Manual feat selection is close to meaningless
Meanwhile, when I browse the core monster manual, I see a lot of monsters are picking these feats whenever possible (especially when they have fighter levels). I am wondering, how bad could they be as a choice of feat selection?
The Monster Manual authors were bad at the game.
No, really, they straight-up admitted it. Mike Mearls talked about it while offering unofficial errata to the Complete Warrior hexblade class. How early on (Monster Manual is even earlier than Complete Warrior) they badly overestimated the value of some things (e.g. attack bonuses), and underestimated others (e.g. non-damage effects like tripping). Sadly, as far as I can tell, this commentary was lost over a decade ago when Wizards ended their “Gleemax” forums (and at this point they’ve purged their site material 2 or 3 times since).
Beyond that, Monster Manual authors weren’t trying to make optimal feat selections in the first place:
Monsters are meant to be defeated.
Monster statblocks are meant to be usable by a DM who hasn’t necessarily prepped for the fight, so anything that can be baked into the statblock and require no additional work on the DM’s part is very, very good, and anything that requires the DM to do extra work—especially looking something up in another book—is very, very bad.
Monsters get special unique features as a matter of course. There is little reason to worry terribly much about feats per se when you can just slap any arbitrary ability onto a monster—in fact, it’s better this way, since your special ability can be unique to this monster, and the rules for it are right there in the description and not somewhere else.
See the Tarrasque for a truly ridiculous example: its statblock has it taking Toughness six times. Toughness is another terrible feat, and no one would ever recommend that a PC takes it six times—but for the Tarrasque, it doesn’t really matter,¹ because its monstrous ability scores, carapace, and regeneration are independent of its feats.
So looking at Monster Manual isn’t really helpful for determining the quality of a feat.
Looking at example NPC statblocks is arguably worse—everything about monsters applies to those, too, except they didn’t even get much love or attention in the first place—they often have outright mistakes. The official, “iconic” example characters for several prestige classes don’t even properly qualify for the prestige class they’re supposed to be an example of.
But we can still consider the question of Weapon Focus et al.
The above is why seeing Weapon Focus on a lot of monsters doesn’t mean Weapon Focus is good—but just because we have discounted one potential source of evidence for it being good, doesn’t inherently mean it’s actually bad.
It is, of course. The above just doesn’t demonstrate it.
The restrictions on Weapon Focus are negligible
Almost every warrior optimally focuses on one specific class of weapon anyway. A trip-lockdown build needs a weapon with the reach and tripping qualities, so they have to use a guisarme unless they’ve burned a feat on Exotic Weapon Proficiency for a spiked chain (or kusari-gama or meteor hammer or rope dart)—and if they have burned a feat for that proficiency, they really want to use the exotic weapon they’ve paid dearly to become proficient in. A mounted übercharger will pretty much never use anything but a lance willingly. Etc.
Furthermore, random weapons you find rarely match what your build needs, and often involve choices that makes sense for NPCs (easy to run), but are suboptimal for PCs (similar story to monster feat choices). For instance, straight enhancement bonuses—very common to see +2’s, +3’s, but it’s not optimal to ever go beyond the required +1. So pretty much every optimal warrior is wielding custom work, not using what they find.
And finally, because of the immense expense of magic weapons, back-ups are rarely viable, so being locked into one type of weapon (and its damage type) doesn’t really matter so much—it’s not as though you can really do better by switching to a back-up anyway. Better to just overwhelm the damage reduction with the superior weapon—DR values are rarely very large. When they are, don’t you have a cleric or a wizard to cast a spell to fix that?
So it doesn’t really matter that Weapon Focus locks you into one specific weapon; you probably were anyway. This is not why Weapon Focus is bad.
But so are its benefits
A +1 bonus to attack is almost nothing. A +2 bonus to damage is even less. AC scales very poorly in this game, so accuracy is rarely something warriors have to worry very much about, and damage scales very well, so high-level warriors are routinely dealing dozens of damage per attack.
At lower levels, obviously, these numbers are relatively larger—their lack of scaling is a big part of the problem. They’re “balanced” against the very lowest levels of the game, so they fall behind—badly—after a few levels are gained.
Opportunity cost is everything
So Weapon Focus’s explicit limitations are negligible, and while its benefits are pretty negligible too, they might be OK, ish, at very low levels. So why the hate?
Because they cost a feat slot. Having Weapon Focus means not having some other feat. And some other feat could do so much more.
For instance, Complete Champion’s Knowledge Devotion, for a very straight comparison: it grants a minimum of +1 to attack and damage, and there is the opportunity for it to scale up to +5 attack and damage. For one feat. It does require 5 ranks in a Knowledge skill (i.e. it can’t be taken at 1st, except maybe if you’re a cleric), and requires more ranks in various Knowledge skills if you want it to scale, but nonetheless it’s Weapon Focus plus 50% of Weapon Specialization, and it isn’t even restricted to a single weapon type (not that it matters very much).
But Knowledge Devotion is not exactly an amazing feat. Amazingly better than Weapon Focus, certainly (and certainly amazing to get for free, as many characters can since cloistered cleric dips are optimal for so many builds), but probably not a crucial part of anyone’s build.
Rather, most builds rely on very specific feats to do their thing. Trip-lockdown requires Combat Reflexes and Improved Trip; without them, you’re not a trip-lockdown build. Überchargers require Power Attack and Shock Trooper (and probably Spirited Charge, Leap Attack, Battle Jump, etc.). Can’t dual-wield without Two-Weapon Fighting. Can’t do archery without Precise Shot and Rapid Shot (plus, if you’re using a crossbow, you need Rapid Reload; if you’re throwing, you also need Quick Draw). Can’t fight unarmed without Improved Unarmed Attack. The list goes on and on—pretty much every PC warrior lives and dies by their feats.
And what that means is that taking Weapon Focus means not taking one of those crucial feats that makes your character do the thing that your character is supposed to do. It makes you slightly better at attacking, but that’s nothing compared to having a viable combat strategy online. And most strategies will consume as many feats as you’ll give them—even fighters, with their many bonus feats, can usually keep throwing feats at the specialty to make it better—and usually should. The game rewards specialization heavily.
Which means that you always have something better than Weapon Focus to take. Either it’s early, and you still haven’t gotten all of the crucial pieces that make your character work properly together, or it’s later, and Weapon Focus is a very paltry improvement to your accuracy.
Don’t forget non-feat considerations
Fighter is a poor class—because class features should be better than feats. The class features of many classes are—rage is a lot better than a feat, for an easy core example. Usually, 1-2 levels of fighter are considered the absolute maximum—a feat per level is OK if you’re desperate, but a feat every other level is awful. Dungeoncrasher, from Dungeonscape, makes fighter 6th viable, but also replaces your bonus feats at 2nd and 6th, so you only get 2 bonus feats from it.
Which means that imagining yourself with eleven bonus feats as a fighter 20th is a mistake—you won’t, or at least shouldn’t, ever get anywhere near there. Getting 2 bonus feats out of fighter is about the maximum. And feat chains are long, so that won’t be enough to “run out” of feats before Weapon Focus becomes meaningless—and even if you did, it would just mean “take fewer fighter levels then!”
Player’s Handbook II
Player’s Handbook II seems to have gotten the memo, sort of, and tried to add more to the Weapon Focus line to shore it up. It adds Melee Weapon Mastery, Ranged Weapon Mastery, Crushing Strike, Driving Attack, Slashing Flurry, and Weapon Supremacy to the feat tree. Crushing Strike and Driving Attack are poor, sadly, and the Weapon Masteries are just unnecessary for most, but Slashing Flurry and Weapon Supremacy are quite good—or would be if they were stand-alone feats.
But since Slashing Flurry requires Weapon Focus, Weapon Specialization, and (Melee or Ranged) Weapon Mastery, it doesn’t cost one feat, it costs four (and mandates fighter 4th unless you’re a warblade).
And Weapon Supremacy, on top of that staggering fighter 18th requirement that no one should ever hit, requires every other feat in the Weapon Focus tree. Even for a fighter 18th, six feats is a lot.
If you were forced to play a single-classed, non-dungeoncrasher fighter using only Player’s Handbook and Player’s Handbook II, then maybe Slashing Flurry and Weapon Supremacy start looking decent. But that’s a rather contrived scenario, basically forcing you to get tons of bonus feats while restricting you to an environment with very few feats to take.
- The Tarrasque is, unfortunately, not designed super-well, since its lack of Intelligence, flight, or teleportation make it relatively easy to contain at that level, and design oversights—i.e. its inability to attack incorporeal or ethereal targets and its lack of immunity to ability drain—mean it can even be defeated at very low levels, but these problems aren’t caused by its feat selections. Better feats could, obviously, mitigate some of those weaknesses, though.