Did some plodding on the Test Server curious to see if things had changed. My targets were Glen Crabs in Grauberg[A]. I did 2 sets of 10 mobs, first full-timing Enhancing gear, second in melee gear with no other DA sources on. I was RDM/BLM, so no DA trait there.

Temper: 459 Enhancing full-timed.

Crab 01: 6/34 = 17.6%
Crab 02: 4/34 = 11.7%
Crab 03: 6/30 = 20.0%
Crab 04: 5/39 = 12.8%
Crab 05: 6/35 = 18.1%
Crab 06: 4/41 = 09.7%
Crab 07: 3/35 = 08.5%
Crab 08: 1/35 = 02.8%
Crab 09: 4/31 = 12.9%
Crab 10: 7/45 = 15.5%

Total: 46/359 = 12.8%


Temper: 459 Enhancing on-cast, 392 on-strike.

Crab 01: 5/36 = 13.8%
Crab 02: 5/45 = 11.1%
Crab 03: 6/41 = 14.6%
Crab 04: 4/41 = 09.7%
Crab 05: 5/43 = 11.6%
Crab 06: 8/46 = 17.3%
Crab 07: 7/48 = 14.5%
Crab 08: 7/30 = 23.3%
Crab 09: 6/44 = 13.6%
Crab 10: 4/42 = 09.5%

Total: 57/416 = 13.7%
Inclined to say the spell's improved, and that its potency is hopefully determined on-cast as opposed to on-strike. If we want to assume that and combine the two tallies, 13.29% would be the current estimated proc rate at 459 skill.