If a battle linkir dies in one round, psions that had 2 health do not always die (because they were older) but instead end the round with 0 health.

this seems like a pretty clear bug to me, but seeing as how cleanup only happens once I don't know how to fix it.

Cleanup should happen more than once, and already does with some cards. Cards that deal damage when they die, like putrid zombie, kill the things they hit. Linkir just needs to be hooked into that mechanic.