That totally depends on how much damage you are dealing....yeah, if you are just standing there fighting one mob then it was a nerf....but the more damage you deal, the more healing you get now.
I believe the old fel armor was 2/4% health every 5 seconds. I'll use easy numbers to make this easier for me, so assume 100k hp. that means 2k or 4k health every 5 seconds. that comes to 400 or 800 HPS. with the new fel armor, you get 3/6% damage as healing. which means 400/.03 or 800/.06 = 13.3k DPS.
13.3k dps and new fel armor heals for the same as old fel armor. anything more, and new will heal for more....currently I don't raid on my lock anymore (he's my old main, and has only been 85 for a week or so), but even in just heroic dungeon gear I pull more than 13k easily...doing TB dailies and dotting up every mob I need to kill for each quest at the same time I've seen my dps hit over 15k....
For pvp, idk....I don't pvp on my lock, but for pve that dps point where new fel armor>old fel armor is pretty easy to achiev.
If you don't like my numbers, here's a web page I just did a google for, showing graphs for 100k, 120k, 140k, and 160k max health and dps.
http://felfire.com/warlock/fel-armor-remake/