So I finally found whats making it impossible, for any group that has me as healer, to defeat Shadowcaster.
Intensify Spirit
- Your Critical Heals increase the targets maximum health by 10% for 15 seconds
This is a talent that works on Revitalize, Crimson Chain and Dark Prayer. Crimson Chain beeing my main source of healing and is used to keep everyone healthy at Shadowcaster. Crimson Chain/Dark Prayer will then apply Intensify Spirit to our tank from time to time, and when Shadowcaster steals that buff he gains 10% max HP but also 10% more current HP. If he dont have max HP already, he wont lose the extra 10% current HP when Intensify Spirit runs out on him.
So if Shadowcaster has 1m hp left and gets Intensify Spirit he gains about 128k HP as about 10% of his max HP. Basicly healing himself up to 1.128m HP. When buff runs out he would stay at the HP we took him down to again. Which sometimes is less than he healed for.
3 times now, have I been in a group and taking him down to 900k HP before he wipes us. While other healers have beaten him.