KidSnide
Adventurer
Something that I learned from 2e and this was reinforced by 3e: you cannot balance combat with non-combat elements. It doesn't work. Why would they? You cannot control how much of either you will experience in a given campaign as a player.
Sure, the DM could step up and say, "Ok, the campaign will have this much combat and that much non-combat" but, that's typically pretty broad and often not too accurate in the small scale. Sure, you might have two sessions of no-combat, but, then you have three sessions which are combat heavy.
Which means that the guys that are balanced with combat vs non-combat elements are bored half the time. The combat wombat can contribute virtually nothing mechanically (although through free-forming he might do better) to the non-combat scenarios, and the Peasant with a Spork is sitting in the back playing with his Iphone during combat because he can't do anything.
The biggest issue I have when you try to balance combat with non-combat is that you wind up with players playing different games at the same table. The gnome illusionist is simply not playing the same game as the human fighter. I don't think that's a very good idea.
Balance like with like. Thus, combat effectiveness is balanced across class and siloed away from the non-combat stuff. The one hit wonder character where you are really good at one thing, be it combat or non-combat, is a bug, not a feature.
I agree with this 80%, but the remaining 20% is also important.
Balancing combat with non-combat is tricky, as you say, because (1) different campaigns allocate time very differently between combat and non-combat, (2) different campaigns allocate time very differently between types of non-combat (wilderness exploration, infiltration, engineering, politics, NPC persuasion) and (3) even within a campaign, different sessions will focus on different types of activity. Because of all these factors, what's balanced for one campaign could be very imbalanced for another. As such, I agree with the siloing philosophy where characters should all have some combat capabilities (because some combat is important to 90+% of D&D) and some non-combat capabilities.
That's the 80%.
Players shouldn't be playing different games at the same table, but they don't need to be equally good at all phases of the game. It's OK if the barbarian shines more in combat than the illusionist, so long as the illusionist has something to do during combat and contributes meaningfully to the party's efforts. Similarly, its OK if the illusionist shines more in social gameplay, so long as the barbarian has a way (perhaps a limited way) to contribute so roleplaying with NPCs in a positive way.
-KS