I've recently committed to playing in a Pathfinder game, and I've become somewhat intrigued with the idea of playing a rogue/sorcerer multi-class character. I'm concerned, though, that as the game progresses I won't be able to keep up with my straightclassed party members in terms of damage output and survivability, essentially becoming a novelty character with a few parlor tricks and no real staying power ("pick this lock and then stay out of the way until we need you to cast detect magic on the loot").
That got me thinking: is there an effective way to identify class combinations which seem appealing up front, but which will fall behind as the characters level up (without actually taking the character through its paces in a game)?
I'm making a couple of assumptions here (NB, I'm limiting the scope of the question to core classes): first, that there are class combinations that DON'T scale well together into the mid- to late-game (if every class combination is equally (in)viable, this question is moot).
Second, that the definition of "working well together" precludes the necessity of min-maxing and shoehorning a multi-classed character into one specific playstyle ("this build works great as long as you only use sneak attacks"), though some combination will of course suit a style of play particularly well (you probably won't play a wizard/rogue if you're looking to be on the front lines and soak up punishment, for instance, but you might try cleric/fighter).
And finally, that a multi-classing character will limit the number of classes taken to two. It seems that multi-classed characters who take more than one additional class start to suffer from lack of focus.
Best Answer
Thou shalt not sacrifice caster levels.
As the golden rule of 3.5 multiclssing, it's hard to beat the above. It's quite possible to apply requirements gathering methods to 3.5 as well as 4e, and estimate approximate to-hit and damage at each level.
Plan out your character to 20.
To answer:
is simple: plan out your character to level 20. Identify, at each level, what benefit the character is deriving from your choices. Test against the requirements given in your requirements step. This way, when your character shows up in game, you have an idea of your intent and the capabilities of the character.
To answer what classes synergize well:
Non primary-casting classes tend to synergize well.
Given that most aspects of a level up are cumulative with prior choices (BAB, feats, HP) you want to avoid class features which depend on your level in the class. Therefore, avoid class features which have level as a variable within the feature.
Rages from barbarian are fine. You get more as you level up:
but you don't have the benefits of the rage reduced (proportionally to your compatriots) as you see in spells.
For the casting classes it's certainly possible to combine them in "gishy" characters (spell-slinging fighters) but they require a specific focus into the combination, preferably enabled by appropriate choice of prestige classes.
So, if you fail to raise rogue, you don't get as much sneak attack bonus damage, but if you're increasing fighter as the other class, you get a higher BAB to compensate.
Whereas a rogue would effectively be writing off "improved uncanny dodge" due to multiclassing.
Therefore, a good combination can be fighter/rogue, because each class brings a separate thing to the table, without having a significant opportunity cost for choosing the other. Other good combinations are those that lead up to exceptional PrCs, which combine features from both classes in useful synergy.