I have a lvl 27 alt constently facing lvl 32 varium players. My goal is to lower them down to 40HP and then bunker and hope it crits. It works alot (I actually have a 87% win rate on my 27) But I imagine how annoyed the lvl 32 will be. i personally think the 25% chance to crit is a little too much as even bunker without crit is a powerful skill.
personally i h8 it when ppl crit me on a bunker even when i have, say 30 more support than them. Also it is effective even for ppl with low tech if they crit.