It just does the displayed damage (which increases with skill level). Like some other skills, it doesn't say anything about weapon damage or weapon DPS, so it doesn't get any boosts from your weapon or strength (which makes it more suitable for setups that don't have much strength or 2-handed weapons).
Buuut this does elemental damage, and focus increases ALL elemental damage, be it from a weapon or skill or whatever, so focus increases that.
There are three types of people in the world: people that can count, and people that can't. "I hate when someone quotes himself in his sig." -Me