Combat isn't the only way to make a class feel unique. The druids is my favourite class as of now, because of the roleplaying options in the grove and the fun you can have with animal shapes. For rogues, I'd expect they get their "faction" once the game moves to Baldur's Gate city. In original BG1 there was a fun questline involving the local thieves guild which required having a rogue in the party, and doing those side quests changed your standing with the guild and the outcome of another quest.