cooldown isnt how much time left after the skill expires, if so it would mean that lots of skills such as frenzy dont have cooldownTechnically its a 30 second cooldown seeing as it lasts for 15 seconds so more like 30 not 45
it has cooldown of 45 secs, it lasts for 15, if u used it and it expires, u will have 30 secs more to wait until cooldown is over, if it was 30, then technically u could use reaper's touch twice in one min