"No, you don't need expertise, your dps/threat sucks because you only Shield Slammed 12 times in a 3 minute fight."
Anyways, back on topic:
For what it's worth, raid finder has this item marked as a tanking item (wanted to give this a shot with SMF, but nope tank had role bonus).
Edit: Who am I kidding, I wanted this to tank heroics with.
I don't think the question is if it will do more damage for tanking. Higher str and higher weapon dps/damage make that a given. For me the question is, is the loss of survival stats on mandible worth the gain of the self heal. I don't think their will ever be a concrete answer to that question though because it involves so many factors.
Personally I'll probably end up comparing the souldrinker heal to a loss of ~262 avoidance and see which numbers I like better. ~194 avoidance from dodge/str/reforged mastery and 68 mastery that frees up mastery on other gear to be reforged. But more than likely I'll pick up the souldrinker and use it. I'll be doing my math on that later though cause I just finished finals and my brain hurts.
One interesting option from gearing I've seen (think it was kopcap) is going max mastery and converting all excess CTC past 102,4% into stamina with gems. So you could also give the loss of ~262 avoidance a stamina equivalent. Still not quite sure where to go with gear atm but it's at least one of the options to keep in mind.
I can see the weapon being great on ultraxion where the extra dps/heal is nice and you already got 100% shieldblock uptime. Other bosses the hc beth sword might be optimal.
Well once you've got full CTC increase in parry and dodge are marginal and due to your massive passive damage reduction Stamina's EH scaling becomes much much nicer. From a healer point of view you now have a huge buffer and a steady damage income.
I thought to point out to those who wanna give these to their DK's and SMF warriors, "1 is enough!". Having 1 in mainhand is a nice dps boost for them, getting another in off-hand is only 50% of it's dps value (assuming those procs get the same dmg penalty as normal offhands do) so it's a waste giving it as offhand to DK's and SMF warriors if your tank still needs it!
This I believe, but have yet to see numbers to prove it though. Would be nice to see someone test it out by putting it in your off-hand for a fight and log it for us.
A DK in our guild was also telling me about a thread on EJ (iirc, could be elsewhere) where they proved the proc to be a 6-700 dps increase as Mainhand. If it does 800+ dps for a tank, it's not a bad idea to increase the raids overall dmg to just hand it over to your tanks :D
I've passed on two already though (1 for pala tank and other for a DK) as I'd go below CTC cap, I'm still using heroic mandible. Now I'm seriously thinking of taking next one, even though we still have 1 DK drooling over it.
Your wrong on the 1 is enough thing. for a start BOTH DW strength classes have passive abilitiels/talents that decrease the OH damage penalty but more importantly the damage reduction for OH strikes does not apply to the proc from souldrinker, as the proc chance is based on weapon hits, and the damage is based of HP. it doesn't matter that the OH weapon skills suffer a damage penalty, all that matters is that an OH attack connects. For a frost DK this means that an OH SOuldrinker isn't as much of a boost as a MH souldrinker since Plague strike doesn't utilise the OH, however DKs generally spend very small amounts of their time PSing, most of there time is spent OBing, FSing and HBing, and OB and FS have the same chance to Proc a MH souldrinker as an OH souldrinker. SMF fury is not gonn have quite the same parity as almost 50% of a warriors GCDs are spent Bloodthirsting, which doesn't include an OH hit so won't proc the OH, neither will HS or execute for the same reasons. so its only OH swings, Slams, and Raging Blows which can proc an OH souldrinker. So yeah for Frost DKs it's still pretty damn good as far as OHs go.
Picked up the 390 raid finder version last night. This. Thing. Procs. Like. Crazy. I love it.