No, not mechanically. He has come down with "guard syndrome", and the prognosis is not good. I was soloing Volenfell on PC NA (in case this matters) and "killed" him (aka brough him to where he summons the gargoyle). Problem was, he was still up.
Killed the gargoyle, despite it being stuck on the ledge above us, while under fire from the boss. Gargoyle dropped, but Quintus was still rocking at 0/1,495,000 ish health.
Tried again after a reset (let him deaggro). [LUA] Quintus Verres (158.8s) - 1,503,293 Total Damage (9589.8 DPS). Still alive. He only has 1.49M health, fyi.
Dungeon breaking bug, ZoS.