Long time no Splenda.
I noticed you were summoning two people for it, you might want to just summon one if you're going to summon at all. Each phantom you summon makes the boss have more hp, so if you have two they will have SUBSTANTIALLY more health. Sometimes it can actually be easier to do it yourself or just summon Solaire to let him tank one while you kill the other.
For the longest time I thought this scene from Wayne's World was the actual music video to Bohemian Rhapsody.