What should I consider when levelling a multi-classed character?

Question

Following up on my last question about a Shadow Monk/Assassin Rogue character. What's the best way to pick which class to level up in a multiclassed character?

Is it better to stick with one class until you get all the class benefits you want? Should you just stick to the stat increases (4th, 8th, etc)? Or alternate (up to a point) to keep the class features even?

I would like to clarify that I'm not aiming to utterly min/max my character. I'd just like to know what're the most important things to think about when levelling in this way - specific class features, ability score increases, or something else?

Also, my character concept is just an example so answers that cover multi-class advancement in general are good too.

If it makes a difference and for anyone that's interested, I'm thinking of ultimately aiming for a Monk 15/Rogue 5. The later Monk features don't stand out too much to me and the Rogue's 5th Level (Uncanny Dodge) seems better for survivability than the ability score increase gained by a 16/4.

Answer 1

If you care about skills, Rogue gets you 2 more skill profs (plus Expertise for two of the four), Thieves' Tools prof (possibly with Expertise), and Dex/Int saves are probably more useful than Str/Dex. Also, Rogue starting equipment is far more generous.

I think your best bet would be 1 Rogue, 1 Monk (thereby getting Flurry of Blows and Sneak attack, unless I'm missing something), and then 4 R (for Cunning Action, increased Sneak attack, Uncanny Dodge, and ability increase). Then Monk all the way.

It's hard to offer more general guidelines (other than grab a level of each first, to get a taste of how they feel and access all your armour and weapon proficiencies, according to the criteria here), because optimal considerations depend on the classes in question (i.e., the feature progression of each class). Some classes give you a lot of value early on, whereas others pay off later. Anyway, I can share some more specific considerations, pertaining other multi-classed characters:

1. A Sorcerer/Wizard/Warlock dipping a level of Life Cleric get plenty of value really early because you'll have access to the most powerful healing (barring an actual Life Cleric), until classes with native access to healing get their higher-level healing. So, for example, our L2 party has a few Bards, all of which grabbed Cure Wounds--even with their 2 levels in a class that has built-in healing, my Sorcerer's 1 L dip into Life Cleric provides more effective healing (until they get Mass Cure Wounds, of course...). Some of this value remains as you level up, given the ability to cast Cure Wounds using higher level slots (which grants an extra 1d8 + 1 per level of the slot, given Life Cleric).
2. Grabbing 2 levels of Rogue, even if it costs you a feat, grants you A LOT of benefits: Sneak Attack, Expertise, Thieves' Cant, and Cunning Action. IMO, these features alone are as good, if not better, than a feat. And that's not counting the proficiencies from grabbing Rogue at L1.
3. For a Charisma-based character, 2 levels of Warlock get you Eldritch Blast plus two invocations (suggested, Agonizing Blast, for +Cha Mod damage on each hit; and Repelling Blast, to move enemies around), and two L1 Slots that recover on a short rest (not to be underestimated, since all Cha-based characters are casters). When combined with a level of Life Cleric, you'll get some free healing after every short rest.
4. Grabbing 2 L of Bard will let you add half your prof bonus to all ability checks, including Initiative. While I disagree with this design choice (if it isn't an oversight, since it expands the scope of JoaT far beyond what it has been, traditionally), that's them apples.
5. Really sweet benefits that come later: Diamond Soul (Monk, 14); Dragon Wings (Draconic Sorcerer, 14); 2 extra ability score improvements (Fighter, 6 and 14; Rogue, 10); 4 spells from any class (Bard, 14); Persistent Rage (Barbarian, 15); Superior Critical (Fighter, 15); Purity of Spirit (Devotion Paladin, 15); Soul of Vengeance (Vengeance Paladin, 15); Blindsense (Rogue, 14); Slippery Mind (Rogue, 15); Create Thrall (Great Old One Warlock, 14); Chains of Carceri (Chain Warlock, 15).

Answer 2

If you are really not aiming to min/max then this is a role-playing question.

It seems to me that you have 2 options, the dabbler and the mid-life crisis.

The Dabbler

This character doesn't know who he is or where his life is going. He does a little of this a little of that without a great deal of focus or planning. This guy takes a level here and a level there until he has an epiphany and settles down into a single career.

The Mid-Life Crisis

This character knows what she wants out of life and has her goals clearly before her. She is happily pursuing her career when something makes her reconsider everything. Perhaps a close friend died, perhaps she was exposed to new ideas, perhaps she became acquainted with someone with a different calling who she admires etc. From that point on she persuades her new career with dedication, maybe even slightly embarrassed about her miss-spent youth.

Answer 3

For this I would get a taste of each, then go get an ability score increase.

So lets say you decide Rogue is the best class to start with (I don't have my books with me right now, I can't say which is better). I would start with a level of Rogue, and then take a level of Monk at L2. This will suffer a bit since the rogue really gets going at L2, but I think it's important to make sure you pick up a bit of each class so you have the flavor working early on.

For third, fourth and fifth levels, I would go right back to your starting class. And then from there switch back for 3 levels. Then take the last level of Rogue. Finally fill out in Monk.

The important thing is to not fall more than a level behind in ability score increases. Especially since you'll be relying on Unarmored Defense for your AC at least until late when magical armor might be better, make sure you don't miss out on boosting your Dex and Wis.

You also don't want to miss out big class features early either. Make sure you focus your first five levels in one class so that you have a well developed character by L5. So I would not have myself spread beyond 4/1 at that point. Maybe if you really liked a L2 feature on your second class (perhaps if you go Monk as your primary, and want to take Rogue 2 early on), you might go 3/2 at L5, but make sure your L6 is that fourth level so you get the ability increase.