What if Cho'Gath feast worked like how it worked in Invasion?
Instead of doing the damage instantly its like Tahm Kench Devour where cho'gath suppresses a champion inside himself.
the Champion chogaths eats are stuck inside his stomach taking damage over time (values the same as LIVE damage but spread out over 4 seconds) If Cho'Gath takes at least 30% of his max HP he spits them out prematurely .
I think this might the keep the 1k Feast instakills from happening during a teamfight assuming the enemy team is aware of their allies positioning .