Now, with the changes to the talent system, talents can be shuffled almost constantly; Holy Prism, self-targeted, is perfectly adequate for trash and otherwise consistent AoE need. For bosses (in LFR; I typically don't have the opportunity to swap in 5-mans), I do change to ES for most fights. I will give you potential gear disparity, but in LFR and 5-mans, I've been soundly out-DPSed once, I believe, by a mage, across both heavy AoE and single-target; other than that, I've only seen steady competition as with that monk, a Blood DK and an Ele Sham in 5-mans, and a fellow Ret in LFR.
I will also give you that my experience is not in true prime content; hoping to rectify that as soon as possible. But I refuse to believe that we are as gimped as you seem to be suggesting in the face of what I have personally seen thus far. I was actually tanking an heroic the other day and got a Ret, a Fury, and a Fire Mage for DPS; every single pull, the Ret was top - AoE, ST. And he was comparably geared to the mage; warrior was fresh 90, I think. Could just be a case of a bad mage, sure, but I would rather choose to believe in the potential of the Retribution spec in the hands of a capable, and competent player than think that all the DPS I've seen in LFR and heroics is just that bad.
...Though I will admit, that is just as feasible.
EDIT: Want to go ahead and apologize for anything in that last paragraph that someone might take offense to; it was not my intention in any way to potentially insinuate that anyone here is bad. Was in a rush as class was ending and wanted to go ahead and get that post up before I left.