I think todays "spiky" damage is fun and there is very significant difference between WOTLK spikes and Cata. The core thing in Cata healing is that you have powerful tools instead of slaky spamming rotation. I have been playing Priest since vanilla and I never had such diversity in spells. If I'm in mana saving rotation I can perform about 4k HPS on single and feel endless like WOTLK paladin)But if I need to, I can use 2 flash+ grater and burn about 9k on single. So returning to spikiness, in WOTLK you’ve got to heal before think, because you don’t have tools to correct the situation, and spiked load from boss can kill the tank. It Cata you need to think before heal, cause your mistake in chousing spells can cost you a party. Spikes in Cata is not a big deal, cause you can thrown HWchastise, flash, and boosted grater and it would be over 45k per 5 sec. So mechanic of the fight force you to THINK and if mob becoming red and big, you should start to cast graters, and if you see, warrs blast wave animation, you probably should cast mana efficient spells, cause if you don’t – you dead.
That’s why I want to state: Spikes are fun!
All figures taken from 85 lvl priest, during heroic dungs.