I'm close to getting a 4th level of Assassin Rogue with a character I'm playing and I'm torn between picking up the Alert feat or improving an Ability Score (i.e. +2 Dexterity) so:
Which is best, an Ability Score Improvement or the Alert feat for my Rogue?
Obviously the main ability scores are important, but the potential is there for me to ignore ability score increases entirely and focus on feats exclusively.
The Alert feat, in my opinion, gives some great advantages for almost any class:
- You gain a +5 bonus to initiative
- You can't be surprised while you are conscious
- Other creatures don't gain advantage on attack rolls against you as a result of being hidden from you.
The initiative bonus is pretty self explanatory - a high Dex character gets a decent shot at going before almost everyone or it could mitigate unlucky rolls.
Practically never being surprised is also a huge plus - you can react to, and potentially even negate, ambushes and sneak attacks against the party.
Finally, preventing advantage on attack rolls against you from hidden characters removes a huge portion of an attacking Rogue's potential to sneak attack your character as well as reducing the chance of actually being hit by all hidden attacks. At worst, if someone gets advantage against you, you'll probably have seen them coming first.
Combining this Feat with the Rogue's Assassin lvl. 3 feature (which my character has) seems even better:
Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.
The bonus to initiative gives you an even higher chance of consistently getting a sneak attack in combat and an auto-crit on the first sneak attack of an ambush can cause huge damage, potentially ending the combat before it even begins.
All of these advantages make me think the feat is superior to the benefits of +2 Dexterity (or another Ability Score Increase).
Personally I don't think the extra +1 AC from +2 Dex (for example) is as good as the benefits of this feat, especially with 5e's bounded accuracy, but I could be persuaded otherwise...
(Edit: My question isn't aimed at discussing which feats are the best. But even so, this feat seems to be one of the best in the PHB and a fairly solid choice for almost any class...)