When tanking at high level raids it's not as big of an issue to bind heroic strike, but the problem you're having now can have the same effect in raids too. Being rage starved is bad and getting in some white hits is good when you don't have much rage, aka: don't cast heroic strike. It's my opinion that it is better to micromanage heroic strike as a separate button, but it's not necessarily a bad thing to do, you just have to use it correctly.
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