in my opinion the set is fine, think about it the set would be ridiculously op with an hp boost.
as pvm currently stands u have 3 weapons that hit stupid amounts i.e tbow, sythe, and sanguinesti staff, why would u want to make pvm less interesting and more afk compared to being a bit more challenging and not afk so players are actually engaged in the game.
for pvp, what is to stop one of these players who own it to combine it with divine or demonic ss and just camping smaller players. sure if u are manage to be killed ur dying for billions, but the chances of anyone killing a player in a already op set with more op gear with that set (divine, split tooth, pegasions, or whatever else) probably an op special weapon is little to 0.
set bonus it currently has, if it is 15% as I have been told it could be. this bonus would need to be removed if it gains a health boost for the reasons I put above.
at the end of the day it is a what 300$ set so it should be op but in my opinion its one or the other, health boost or its current boost.
as for the arguments with ancestral and justiciar having hp boosts, those items are best in slot for players who aren't willing to pay 300$+ I think it has appeal for a player to again be engaged in the game and its grind. I think as much as the devs should be pushing out their p2w side and making money, they should also balance the game and its end game features and make it so its not all about donating.