first off sry for my bad english
well i think the main problem with the mana regen in WotlK is the same as in TBC. on low tier raid instances the dmg the MT take is realy low compared to later. you could heal the tank realy easy and there are no real probloems. nnow in the next raiding tier the tank have more equip and some awsome avoidance. the only way to solve the problem that it should be challenging ist to let the boss to hit harder.
And ich think personaly exactly now is the difference between WotlK and TBC becouse of the abilytis of the bosses. aloste every heavy healing fight in ulduar alredy got a "i kill your tank without CD style". so they cant let the bosses hit hardy becouse it would be an instant death without a chance of survive it. so blizzard just cant make the upcomming bosses just more challenging becouse he hits for more. so the only way to improve the challange is over manaregneration.
almoste all paladins say we need to spamm HL becouse the tanks need it.. well yes your right.. so you cant keep up the tank so you need DP rotations.. maybe healers switching to the tank in some moments and so on.
i think bliizard doesnt want us to be tank only healer anymore.. i personaly think they want: 1disziplin prist on the tank and 1-2 holy paladins with beacon on the tank but 100% rnd healing.. maybe 1 druidid rolling hots on the tank. that would be 2 support healers, 1 rolling hots on him for steady healing and massiv amounts of shields on him. ithink this is the way it is going.. maybe im right maybe not but is see it that way...
again sry for my bad english.. and thanks for all who still read it :P