I am pretty sure the terror cats are too tough.45 WS, 64m charge, stealth, 1D10+6 dmg, 20 wounds 2 armor and 8 TB? And as many as there are squadmembers? 2 cats almost obliterated my group of 4. how should a starting character survive that encounter? Ok they can't dodge and parry which makes them attack with all out attacks boosting their WS to 75.
If the get the drop on the characters (which the probably will) they are able to kill the whole squad in the surprise round. Infact they are tougher and scarier then Big Mek.