When I write adventures, I design encounters around the traditional "core four" roles - warrior, wizard, rogue, priest. I've found I can waste a lot of time chasing after other classes, and that 99% of encounters devolve to one of the core four roles anyway. (I'm doing a top-down rewrite on my latest for just that reason; I went off the rails chasing down something for Warlocks.)
I've also found it's largely a matter of semantics. You don't have to be a rogue to be proficient with thieves tools, for example, as was pointed out above. You don't have to be a cleric to be an effective healer. You don't have to be a wizard to be proficient with the Arcana skill.
You can just as easily assign the stats to the different roles and design encounters around the stat and the skills associated with that stat. Rather than warrior, wizard, rogue, and priest, you get STR/CON, INT, DEX/CHA, WIS. It doesn't really matter what the character solving the problem calls herself, provided she has the skills to solve the problem.
I think that's what OP was going for. D&D has developed CHA to the extent there's a fully-separate role for it. I lump it into "rogue," because my archetypal rogue, like the Grey Mouser, is charming as well as dexterous, as able to wriggle out of a situation with his glib manner as his rubbery spine. But if people want to split it out into "bard," fine by me!
Cheers,
Bob
www.r-p-davis.com
