Well, Maokai hasn´t been a balance issue has he?
He didn´t receive his technically second rework that still managed to unsurprisingly break him to the point Riot Repertoir's quote from way back("it´s shameful that we´ve kept Rengar in such a state for so long", etc etc) is still valid.
Maokai is supposed to be tanky, hence him being able to have a huge shield because surprise surprise, he builds health as well as MR and Armor. He isn´t even an issue.
Hecarim being able to do almost half a squishy's health bar in damage while having another health bar himself worth of a shield however....