I like keeping ISB up 100% because even when not tanking there is sometimes raid damage happening. I certainly agree we need to have ISB available for Fel Claws, but why wouldn't we? When we can keep it up 100%? I tanked KJ on my monk for the first time tonight. I supplemented ISB with AHR or FB, with a Purify toward the end of each round. Seemed to work out ok.
If there was an option to have ISB auto-renew itself so it stayed up 100% and we only ever saw the surplus brews, wouldn't most of us use that? Just for convenience and safety?