MM yeah I don't know what most people run with, my chance to connect is about 80% and I armoried Kungen and he only had 11 expertise (2.75%) but 7.72% hit so that's around 85% chance to connect.
In terms of the numbers I may have made some mistakes, I put all my formulae in my thread and was using (Damage + 770) x 1.3 for shield slam's threat iirc. It's more likely that if I have made a mistake, it will be with revenge as I get SS and dev in similar ratios to you but revenge is higher than devastate as well as being on a par with SS (in my gear in ICC).
Here's my thread, formulae are near the bottom:
It could be that we're looking at quite different setups in terms of stats/buffs. Are your numbers with or without improved revenge?