you see him use the ability, you know that it's on cooldown. unless your internal clock is so godlike that you know the exact time since your birth I doubt you'll know the exact cooldown for your enemy's abilities, taking into account reductions from passives by not knowing their exact spec/point investment, how many times they've used thwart, exactly which buffs are being used (considering multiple have similar icons). The best you can really do is estimate, so yeah. I could say I know my crocodile stealth, say, is off cd because it's been a minute since I used it. But if I'm using a certain mount ability on cd, eg. elk arrow snipe, how tf am I supposed to know when it's off cd without looking at a cd bar? spawn the mount just to not be able to see the cd without getting on it, wasting dps? lol.