Note that the encounter description (Dark Hunters) says they'll be looking for an easy meal and will flee as soon as one of them is downed. Essentially, this encounter comes down to one question: Can you free your heavy gunner (or operator) from melee so he can take a shot at the kitties? If a ratling sniper, a meltagun weapon specialist or a heavy gunner (or the Operator if he's still in the chimera) make the Awareness test at the start of the encounter, they've got good chances of severely wounding at least one of them during the first round. The cats are not too agile, meaning their initiative sucks unless they have their surprise round.
I'd say the encounter is hard, but quite survivable, especially if the characters are death-worlders themselves or at least have the good sense to listen to the locals about the dos and don'ts. Like "Don't exit your vehicle for any reason whatsoever - bring a bucket if you have to!"
That being said: The adventure says to make an Ordinary (+10) Opposed Stealth check against the characters. This would give the cats a score of 50. Does this take into account their size (Hulking, -10) and the possibility of player characters being suspicious and alert (-10) as most intelligent (=currently breathing) deathworlders would be?