I've (played) watched the map (since basically there is nothing to do, just watch the snipers attack).
I didn't find anything so interesting about this boss fight.
*Beast Master with a Huge Model. Isn't it way to big? Make it a lit bit smalled IMO (Rock minions too)
*Beast Master turns red at 50%. Add him some buff that says that he is on rage and gains attack speed or whatever
*Phoenixs in his hands. I didn't see any difference on his attack, just that he got 2 birds on his hands, but he seemed to deal the same damage.
On the other hand, I found more interesting the ghost fight, when he splits into ghosts minions and then turns back into his real-self.
I don't know how helpful would you find this review, but I hope it helped somehow.