Is fracture even worth using as a DRG?

[Xiroth]

think of it as a 220 potency attack. its good but not amazing

Ah sorry, just looked it up and saw it's an 18 second dot, not 15.

So that's 5 instances of dot damage? or is it 6? Do you get 1 dot tick immediately when you use the ability (A 100 potency hit plus a single 20 potency dot tick at the same time)? Otherwise this would make it a 200 potency attack overall.