Retribution Paladin Weapon advice

Hello all.
I've played a Ret Pally for a while now, and I've gotten to know the class pretty well.
Anyway, I come to you with a problem about weapons in Tier 13.

I'm almost positive this thread has been made already somewhere, but search came back with nothing.
I'll lay it out real simple:
403 Gurthalak, Voice of the Deeps vs. 397 Experimental Specimen slicer

http://www.wowhead.com/item=77191 vs http://www.wowhead.com/item=77217

I've done a fair amount of research an the topic, and most of them say the same thing. Gurth does more DPS, however it's based on proc. Whereas ESS does more consistant damage without having to cross your fingers.

I'm sure someone here can relate to this... However... my RNG sucks (why I'm playing a Ret Paladin, I may never know). It sounds kind of dumb, but it does.
I've recently moved guilds, so unfortunately I don't have any logs since since the weapon was obtained.

All I know is this thing never procs... I mean like 2-3 times total on Ultraxion...

Someone help me out with some input, some reason, something to make me believe that this thing is any good.

Where were you standing at Ultraxion? If you stand further back than the second line from the edge of the platform the tentacle cannot attack the boss.

I was standing right up on the ledge. well, close enough to the ledge.