Regarding Human Weapon Skill for tanking, first remember like Cat mentioned, Yellow Attacks can't glance. (Heroic Strike).
Regardless, this morning I was curious and tested to find out for myself how the 305 Weapon Skill was for tanks.So I went on another server of a friend in our guild and he let me test the distinction between 300 and 305 Weapon Skill with normal prot Talents a 1.9 Weapon Speed, infinite life, full t2, bulkwark etc.
The rough math came out to the 305 skill producing 5500 more threat on Patchwerk for a 4:40 duration with only white hits + Shield Slam+ Revenge+ Sunder and Shield Block on CD vs the 300 skill. Obviously this will never happen as you're going to have infinite rage on Patchwerk.
So I went over to Onyixia to test a more real scenario where you really don't have as much rage and can only afford to do a normal rotation WITHOUT HS.Taking a Timeline from Exiled's Nost Kill with around a 6min fight window, taking out for Phase 2, only counting Phase 1 and 3--I got around a 3200 threat bonus from 305 skill vs 300.
So even on a low rage fight with 0 HS you're really not gaining much benefit at all (3k margin is minimal). anything over a 5-6 minute fight.Still though, you do gain some tiny little extra threat as human. I'd say if you ever think you want to DPS though as a human warrior is a must. Just thought I'd help anyone out who was considering the difference