[Gameplay] Buff or aura consuming large monster

Steps to reproduce:

.1. Tahm Kench, Cinderhulk (Chilling Smite, though that is unlikely to affect this), gromp poison buff, and red buff.

(Also, in case it matters: 12/0/18 masteries - Fury, Feast, Natural Talent, Bounty Hunter; Unyielding, Tough Skin, Veteran's Scars, Swiftness, and Strength of the Ages.

Attack Speed marks, scaling Health seals, 3 scaling MR and 6 scaling CDR glyphs, and movement speed quints.)

.2. Attack blue buff large monster, but do not finish it off with an attack.

Expected result: The large monster goes down to 1 HP but does not die. Auras and Buffs should not kill a large monster. This was put into place a long time ago to allow you to pass a buff to a teammate.

Observed result: One of the auras or buffs kills the monster.