This thread isn't helpful or providing any insight on how to actually improve at tanking. It's just one long complaint about tanks and cooldowns. I can tell you from personal experience the number one reason why I'm not performing cooldowns when I should is because they haven't reset from a prior use. And a prior use could be the result of anything. Maybe an accident or from fatigue. More likely a desperation attempt when I see my party and myself on the verge of death where upon I may pop several cool downs as a last ditch effort. Or possibly just poor timing. Doubtful anyone but the tank knows for sure. Best to make light of it and try again.
S**t happens. You don't point fingers. You do try learn from it and move on.