If that tank is to dumb to notice a sleep that was casted then he shouldn't be tanking. I've been tanking since the beginning granted I don't mark order bc I don't hardly lose hate but when I do I get it back very quickly with no issues. You can sleep and mark the ones u slept but that tank should notice what has happened and should be aware of everything around him 90% of the time. Even with war he should have flash to still aoe Aggro to not wake the mobs.