Yes, all classes will be able to do everything, though with different mechanics.

Nitro is running 8 rogues (saboteurs), mostly PvP I think. A long time ago, I ran a twink team with 1 cleric tank/heal + 4 marksman rogues with pig pets in the level 30-39 bracket. That was pretty awesome. Nowadays I have 7 clerics + 3 mages. I mostly do PvE and sometimes PvP (mostly just to finish PvP quests and keep CQ bar up). The mages are either Pyromancer, Chloromancer and/or Dominators. The clerics are Justicar, Cabalist/Defiler and/or Cabalist/Druid.

I didn't like the pyromancers much until I got close to max level. Now they're pretty decent, with more mobility.