Have you played a ret this x-pac? True enough, you can't just stand still for a minute and keep spamming heals. But you can easily heal up from zero to full, start DPSing and by the time you drop to low HP again, you will have enough mana to heal up to full again. And then it's even easier for feral.
Best part is, why do enemy mobs have mana bars anymore? Its funtastic when you're facing a boss with 1M+ hp, but only 32k mana, yet they never lose a single point of it throughout the fight. Its for looks.
Since when are we shadow priests good at healing? They deliberately took a dump on our healing abilities this expac. Which is fine, because "healing too well" is cited as the main reason our damage is notorious for being below everybody else. Funny that the healing took a dive but the damage didn't go up much.
outside of healng hard cast FoL as ret mana is not even used at all i can remember when everything cost mana to cast before Holypower was introduced