Just finished reading everything. This is BIG. Like destruction of EVO big. This will run a train of shenanigans on this tourney if it doesnt' earn an immediate DQ.
Maybe as your character dies try to do a THC or raw tag in your next character's slot? If it reads your next dude as an assist maybe you are getting the invincibility portion of the assist somehow for your oncoming dude and then essentially guaranteeing your dead point is now considered via a glitch to be "tagged out" even though they are dead. With no health to lose this would mean they can't die if their death is tied to both reaching zero and being hit. Can you die from poison arrows? If not then deaths would need you to be both hittaking a health reducation and THEN reaching zero to occur.
Thats all just theory stuff up there, but if its right then thats why you would get an invincible oncoming dude AND an invincible assist to spam. It'd mean you'd have to put on point your intended assist though so Popping Doom on point and riding it out till he died would be a new thing.