well. yeah. actually.
this game is balanced around max level pve, 3v3, 5v5 and to a lesser extent rbgs.
as much fun as wpvp is ( and if you look in my posting history you will see lots and lots of posts talking about how much i love random bgs and wpvp) they are NOT what this game is balanced around. using them as your basis for a spec's success or lack of success just isn't very accurate.
rets are pretty sturdy when played correctly, but they sacrifice a lot for their survivability in terms of mobility, damage and control which is really the problem, they do well in random bgs and in low to mid range arena due to opponents not knowing how to counter them. in high end arena warriors have traditionally always had better arena rep then rets have.
right now warriors burst harder than rets ( which is really something considering rets have traditionally been one of the most egregious burst kings in this game), have better survivability than rets due to the active nature of ret heals, better control than rets and better mobility than rets.