I'm doing perfectly fine with my full i90 brd. Think is, ranged dps queues are very long.
Apart from that I'm doing PvP on whm and pld (lower levels); queue times significantly shorter here, almost instant. Downside: Less marks as rewards.
Top priority for blm would be swift-sleep the enemies, most of all the healer. And run. You'll probably be main target.
Same es healer, swiftcast is absolutely necessary. Try to hide whenever possible, watch out for stuns/sleep and ranged attacks. If you're going sch, watch the fairy. There are parties who focusing the fairy first instead of the healer. If your fairy goes down, be sure to have swiftcast off cd to summon her again immediately.
When you're tanking, either make perfectly clear which one you're targeting or if you got the time, mark the enemy which you want to be downed first.
Also certain PvP only actions will become unavoidable, but you have to unlock them in doing PvP.