Yes, absolutely proto it out if you're going to use it. Plus, getting some points into Proficiency is really crucial if you want to get through everyone and their armor plate stacking mother.

The Charge is the only variant I can stand to use, personally, since otherwise the lack of alpha damage means that you can really only consistently kill people who are running across the middle of large open spaces. You should try to get the hang of the charge double tap- fully charged shot, ideally to the head, then quickly deciding if you can follow up with a half-charged shot or need another full charge.

The Kalaakiota Tactical is really only useful for counter-sniping for the double/triple tap to the head, though it's definitely great at that. It's my weapon of choice for putting an end to Thales. Against non-snipers it lacks alpha- people will start strafing and hopping after the first hit and generally will be in cover after the second.

The Ishukone (AKA regular) sniper just gets simply out-done by the other two options. Low DPS, low alpha... good for suppression I guess with the big clip size, but it's still just not that great.

The main problem with being a sniper is that it's not a role you can use every match. The map has to be right, and your enemies have to be playing in a particular way- i.e. spending lots of time in exposed, but valuable, tactical positions. IMO the best map for sniping is Fracture Road in Dom- the match almost always comes down to who controls the ledges above the objective, and it's completely exposed to sniping from the rooftops of the complex that is B in Skirmish. Manus peak is good for sniping as well, for obvious reasons. The bridge map is hit or miss depending on how your enemies are playing it, but sometimes it's also a good shooting gallery.

Nope, it's a rail weapon, its proficiency bonus is to armor. *shudders* it would be nearly unusable otherwise.