without any sort of purge/dispell it will be very hard - the mechanic is that the boss puts a buff up on himself, and then it spreads to your party as you hit him and stacks higher and higher - I believe the buff heals HIM and reduces healing done on YOU.

If you don't have any purger then you are going to have to kill the adds imo, don't think you'll be able to burn. Only one person at a time can see the adds so it is going to be rough.