On the Xenomorph critical injuries table a roll of 2, WOUNDED says at the start of the turn a d6 roll of 1-3 it tries to escape. Would that be a MOBILITY roll? And if successful does it simply RETREAT thus incurring a free close combat attack against it? Or does it move further away, a few zones without an attack against it? "Tries to escape" is rather vague. Sorry if I missed something obvious...   

I'd say you only have to make a Mobility roll if its Engaged with another PC (which is the Retreat action on page 59, basically). Otherwise I'd assume it just attempts to leave the area by the shortest route possible, by scuttling into a vent or hiding in the next zone, no roll needed as its a Xenomorph after all. Nothing is more sad than rolling Mobility for a Xeno, rolling no 6s and having it scrabble pathetically at the wall in an attempt to climb it. Though it can only move 1 zone away, because its Speed is now 1. 

I had terrible luck with my first outing with a full strength Xenomorph. It utterly failed to Ambush somebody because I couldn't roll a 6 to save my life, then someone pipped it in the initiative roll and one-shotted it with a shotgun (despite rolling 20 dice for armour) then they got the "Blown apart" crit result. Maybe I should have fudged one 6 on the armour roll so it actually got an action, but I'm too honest, clearly.   

Thanks! Yeah that's what I figured as well. I ran a scenario last night where a bloodburster rolled a 4 on its attack which reads  "TERRORIZING HISS. The Bloodburster jumps onto the victim..." I took that as getting into engaged ranged with the PC inflicting a panic roll, which was passed. The PCs next action was to pistol whip it, inflicting one point of damage, bloodbursters turn comes and having been WOUNDED earlier must roll d6 at start of round, it rolled a 1 so tried to escape, it failed its RETREAT roll(with nine dice!) where it was promptly pistol whipped again. Then boot stomped for good measure...

Yeah, Xenomorphs aren't quite so scary when the Game Mother can't *buy* a 6 on a ton of dice. Still, at least yours was a Bloodburster which are meant to be fairly weak!