After casting Disometric Guard I found out that the stacks start disappearing automatically, without any status effects being applied to Qorvex.
(to test this, I basically jumped into a survival mission, used the ability without starting the mission and watched as the stacks slowly disappeared one by one.)
However on allies the ability works just fine.
I noticed this after playing with the new update, as it suddenly made the stacks way more tricky to maintain.