According to the Cryosthesia lore tab Splicer Gauntlets can be used to throw off Vex targeting. Since Mithrax was there it's likely he was doing exactly that. It could've been shown more in the cinematic, but I'm just happy there's an actual reason for the crappy aim. Edit: Seems like lots of people are disregarding lore released months ago just so they can say "BuNgiE bAd". I get the cutscene could've used a LOT more polish, like Saint not using a bubble or a Banner Shield for whatever reason, and they definitely should've thrown in a line from Mithrax saying he was manipulating their aim, but seriously. Disregarding lore already released BEFORE the cutscene is just dumb.