Question - How to kill a healing ooze

[Darkmax]

I've been working on Grannus the Cleansing Stream, group mission. Burning him down isn't really an issue can down him in approximately 50 seconds. The problem I'm having is keeping him from getting healed by a healing ooze. I've tried both burning through Grannus and targeting the healing ooze when it spawns. So far no luck in stopping him from healing Grannus. So I'm looking for any and all advice on how to handle the healing ooze for the the achievement.

Thanks!

 

[runcade]

Has anyone been able to beat this in tbm group gear with kiss? It seems like no matter what he reflects all spells after 50 percent.