Raast too OP?

when kayn turns into Raast, he against 34.5%-43% health back from all his abilities, i have seen him 1v5 many times, Raast is just far more superior than blue kayn, being a lot more tanky and has crowd control. Its like you get a Darius q, but doesn't scale on your missing health, or how many champions you hit, also don't need to worry about hitting the boarder to heal. he only needs to be a little bit ahead to build full ad with Raast and 1v5. Lets say for example, an OP champ like vayne in late game, stuns him, he just clicks r to gain half his HP back just like that. Right now in season 9, he is one of the most picked champs in gold/ plat and has a top win-rate in jungle with most people only playing Raast and forgetting about blue kayn, its like Ohmwrecker. Seems like too much for me.