Does HS trigger global cooldown? I can't remember off the top of my head. :unsure:
How are you limited by global cooldown when you can use HS to dump rage rather effectively?
Hm. Maybe I'm just a bad tank, but given that a mob has 5 Sunders, Demoralizing Shout, and Thunderclap applied, I cycle through Revenge -> Shield Block while queueing up HS and refreshing Sunder and a lot of the times I have excess Rage left.
For what it's worth, my tanking gear is awful though. 340ish Defense, 7k AR.