I just made some tests with my lvl 90 Necro with 304/265 in specialize alteration. I removed the detrimental mana pres item before testing it:
Pyre of Nos rk. 2 without spec. alteration aug: 1485 mana per cast Pyre of Nos rk. 2 with spec. alteration aug: 1445 mana per cast
= 40 mana less per cast or 2,7% additional mana preservation. If you have a mana pool of lets say 50.000 and if you only cast alteration based spells, then this augment is worth about 1350 mana.
Did a test, 10 casts of Earnest Light in a row without aug, 10 casts in a row with aug... averaged the 10 casts in each group and compared the difference... ~60 mana/cast. Over a long fight thats huge.
not that necro's need more things to allow them to continue casting these days, but took my sk and soloed the raid to get this aug for my necro today. Wasn't too long, super easy for sk skills.
Necro is now 300/260 specialize alteration skill with this on
Sucks we just got done with this one and we were all breaking barrels looking for stuff. I broke a splintering barrel in a wagon and it had two of these augs in it. It was lore so I couldn't grab both...we got booted out that second and the one rotted...oh well:( fun raid though.
These augs are about 2 percent mana preservation... So, yeah, I'd say unless you have all augs with over 600m or more, as a raid healer, I'd guess this is easily the best aug in game for you as of right now.
Would you equip this aug and remove an Anguish 90hp/90mana aug? Will raising my specialization alteration from 260 to 299 be worth removing a 90hp/90mana aug?