Saeviomagy
Adventurer
The way I figure it, any character who wants to be a sniper is already provided with plenty of ways to deal extra damage. My sole goal here is to provide a reasonably balanced way to extend their range to match what any gamer would expect a sniper to be capable of.
For that scenario, I think you hit the nail on the head with your skill power. Sniping isn't something you do all the time (because you only get a shot every other round). It's fairly cheap to get the ability (because it's a skill power 2) and it's going to be there every time you want it(at-will).