There was a patch where they specifically disabled the ability to get 4 pbae's off with a necro. The way I read it, they hard coded a cap of 3 in.
edit... found the patch note
2019-4-4 Thursday disease should properly prevent npcs from regenerating health in all cases relic capture participation is now granted to all players within clipping range of the relic carrier when it is placed into the keep thrust/slash/crush weapons can now drop for reavers /bgchat now works (suggested by the client when using the speech bubble thing) loosing materials while crafting now plays the correct song necro: facilitate painworking is now limited to at most 3 spells, better pet behavior lead to 4 casts being guaranteed in case of full buffs which should not be the case necro: the distance to the pet in order to use RAs is now 1000 (up from 500), LOS to the pet is still required damage shield pve damage has been adjusted lots of instance related fixes lots of mob spell related fixes and more supported spells for mobs