You should do just fine, just won't have quite as much DPS as the 4 or 5x sham teams; but you have a solid healer/tank/3dps group with nice tools for lots of different scenarios.

edit: when i sub in guildies / friends i do just fine with 3sham + pal + [insert random guildmate] and if they are a tanky type that knows how to rolll without CC i just run my sham and drop the paladin.