Rakan's Cooldowns

Rakan's cooldowns seem really, really steep for me... I understand having a high cooldown like on Diana's e aoe utility because it adds a lot of cc for her burst and dashes (which is on a low cooldown), but he has high cooldowns on all of his mobility and cc, and that is all he is. If he is an "assassin support" like I am assuming Riot wanted him to be, then shouldn't he have lower cooldowns or at least some innate constant passive/ability passive that makes him useful beyond his one combo that makes him useless for up to 20 seconds? His poke and heal trigger aren't great and his ability ratios are so high yet he has to go in to accomplish anything and he is very likely to instantly be blown up unless he builds tank, which squanders his ratios.

I'm probably not explaining this that well considering I'm really tired and most likely flawed my own logic, but tell me what you think.