Since you're a tank, I'd say go ahead and get geared out first.

Having flexibility is never a bad thing, though, and the +100% exp bonus (+50% after level 50) will make leveling those others easier.

Also, you don't necessarily need to 'commit' one way or another. If you just need a break from warrior, go ahead and take one and just play something else for a bit. Or if you're really into it and want to be a warrior waking and sleeping, sure, go ahead and focus. The game doesn't really punish you one way or another, even if you don't hit the weekly caps you'll still get geared out eventually.