So I got two relatively painlessly, and just ran around Elwynn for a bit killing mobs. It procced twice in the first two kills and then not again for the next 15-20. Went to hogger for a few and got it to proc twice on him one time.
It scales really well with gear from the looks of what i saw, might scale with weapon damage too? Looking in the journal I thought they were pretty OP but i had the ilvl 44 staff equipped, so it said the drain was 188... turned out to be 133 (still strong) with 2x equipped. I dont think it procs enough to keep you topped off with full talasite like i had hoped, looks like it'll do better in a full agi gearset. Could get the proc up pretty high, i'd think.
Again, not great testing but but general idea of what to expect from it. Didnt get the artifact yet so cant compare.
Obviously not comparable to the 44 staff, but that cant last forever...