Prot-Holy was nerfed significantly with the justification that Paladins healing in PvP should be taking Holy talents, not Prot talents. This has been reinforced with the recent change to Sacred Shields' baseline effect and placement of 'Imp. SS' deep in Holy, though it strikes me as being ass-backwards as far as development decisions go. The knock-on effects are inevitable and have been brushed off by Ghostcrawler under the excuse that Ret is 'too tanky'.
I'm not sure I've ever heard anyone, even in 3.0, say that Ret was too durable. Too bursty, definitely, but never too durable. The last time I can remember anyone bring out that old chestnut was in Vanilla, levelled against the whole class even as it underperformed in PvP and players needed an atlas to find their interrupt (as well as their asses). Indeed, the 'Three Lives' comment has yet again returned at a time when Bubble-breakers have never been more prevelent, and by GC no less. You might be under the misapprehension that a class which needs three lives to down an equally geared adversary has greater issues than these cooldown, I know I am. But I digress.
With Ret's durability being nerfed and burst no longer being the be-all and end-all in Arena PvP Prot+Ret has started making an appearance. The idea seems to be that burst damage is still 'okay' but control is generally better, to the extent that it's more competitive in group PvP. Also, the spec is obviously a hell of a lot more durable than Ret in 3.2 and even more so in 3.3 as SS and hence its' synergy with AoW+FoL is being nerfed.
Mana could be something of an issue even with talented Divine Plea, but look at what you could get.
Avengers Shield - A Ranged Snare or Silence on a 30sec cooldown that deals plenty of damage. Ardent Defender - loads of damage reduction, passive self-rez and expertise 30 Second Hammer of Justice to make up for a lack of Repentence. Damage Reduction up the wazooli, including magical damage reduction and party damage reduction/redirection A significantly larger Hit Point pool.
In 3v3 Arena team Ret's light is declining, as evidenced by the latest SK-100 leaderboard which has Zero (0) Rets. If you still want to play your Paladin in an even slightly offensive role Prot-Ret could be a strong alternative to Ret. Heck, if you want to give it a try all you need is 50g for a respec and a good Sword+Board, though eventually Block Value gear is going to start ot look tempting.
Tentative 53/18 Build, Inc. Glyphs.
N.B. I'm not to blame if Prot is nerfed following this post. Really.