The Cateran is probably THE one best ARO unit in Ariadna. The interesting version here is the one sporting the T2 sniper rifle. With this deadly weapon, you are somewhat on a level with the gold standard of ARO, the MULTI sniper rifle.
The most important aspect of an ARO unit is to be able to do more than one wound per ARO, threatening HI units and those with V:NWI. The Cateran surely delivers in this aspect, even if it comes down to single armor rolls per hit. However, if you crit, that's 2 wounds down automatically!
Adding to this, the Cateran has Limited camo and also Mimetism on top of that, allowing for good face to face matchups, as long as the opponent doesn't bring MSV.
Also, keep in mind, that this is a LI unit and also one with climbing plus! Relocating your sniper has never been so easy as with the Cateran!
The AP CCW is a nice bonus, one that will not be used much though.
Looking at his primary function as an ARO sniper, being irregular is not too bad for this guy. You could stick him in his own combat group and he would still deliver - the lowered point cost for this is also very nice.
Should your opponent have the first turn, Camouflage and Mimetism, as well as good placement (weapon ranges and cover!), are your best chance at surviving. As long as you don't absolutely have to, don't give up your Camouflage in the passive turn! Make the opponent spend those orders!
CC 19 is incredible for a sniper - but don't ever rely on it, especially not when facing real CC units with Martial Arts, etc.
Should those fail, there is nothing more to fall back on - be it armour or BTS... But hey, that's the price you pay for getting such an efficient sniper!
The Cateran is fairly straightforward - just put him in a good sniping spot and that is it. Also, I would not hide him away (so to not provoke AROs) for later active turn usage, unless the opponent has a perfect counter running about (e.g. Aquila Guard).
On the other hand, he is another camo marker - so in an Ariadna camo list, he definitely adds to the charme. You can also place him next to an ambush marker (bring a Spetznazs or Hardcase) and keep your opponent guessing.
MSV units of any level and capable of getting into a good shooting position should have no problem of dealing with the Cateran. The main hindrance is to get rid of the marker status. Specialized CC units like Fidays should also easily succeed, once the Cateran is revealed.
However, it should be noted, that in using up specialized resources to deal with the Cateran, he pretty much served his purpose already.
Thanks to the low point cost, the Cateran fits neatly into a lot of lists. Since he is irregular, using him in combat groups having a low order count is not advised.
His clearly defined role also means that he is perfectly fine to put into his own combat group.
As already said, the Cateran should be positioned in a good sniping spot (a tower, a rooftop, etc.) to generate AROs.
Active Turn Role
Basically nonexistent - if the opportunity arises, a surprise shot from a good position can be neat, but that is not the role of this unit.
This is where the Cateran shines. If placed correctly, a lot of AROs can be generated, forcing the opponent to deal with your sniper before being able to move more freely again.
If he is downed, that is a loss you can take, since he doesn't provide a regular order anyway.