To my knowledge plenty of junglers can do this, and some of them can do it even faster. Also, what else do you expect out of Maokai? Maokai is a utility champion, he's practically MADE to have some of the deadliest ganks. What makes him deadly, or a threat in the first place isn't his damage output, which he doesn't do phenomenal in to begin with, it's the role he plays that makes killing champions easier by means of locking them down and letting your team do the rest. Without a good team comp Maokai really can't offer much aside from fast clear speed, which is useless if it doesn't follow up with successful ganks. If you take away the efficiency of his ganking potential or utility, which works hand in hand with said potential, then Maokai is no longer a good champion because he serves no purpose he can succeed at. He's NOT supposed to be running around killing everything like most champions, he's supposed to HELP the ones who run around killing things to kill things and is unable to do all the work himself. In other words: He's working as intended.