Any pilot ability that deals with crits seems to be 'not that good' as voted by a a vocal minority on the forums. The Defender will soon have two such pilots, Good ol Rexler and Stele. If you don't want to include either pilot in your lists then don't. Personally I think these pilots can work in both 100 pt death matches with minimal upgrades as well as be phenomenal in Epic games. Getting to use those abilities is great, but don't forget to actually fly the **** ship first.
Rexler's doesn't deal with crits (or at least, not on the dice).
He's seen as not that good because you have to spend an action to activate his ability which you can't use to mod dice. And modded dice are how you make good lists.
I've seen Juke Rexler work, and I think he's going to be made better by the twin officer shuttle, but other than PS, he's not an outstanding pilot.
I look at both him and Maarek in Defenders more as pilot skill with a bonus ability, rather than paying huge attention to either ability. They're bonuses, not the central point.