Excuse my blasphemy but him, Boba Fett, and Starkiller from TFU are all over rated characters.
Why all the Boba Fett hate? Calling him overrated is way too harsh, man, come on... You're right about Starkiller though. And Maul, well, he fulfilled his purpose perfectly in TPM, he was always just muscle for Sidious, and that's it. He was never an intellectual and a strong political figure like Dooku, or a promising young "Chosen One" like Vader. Disney have decided to give him a little more personality, by adding more aspects into his game, and IMO have ruined the character somewhat. He was always perfect as a silent cold-blooded assassin, he didn't really need much else. And it was always more interesting to me personally, how he became Sidious's apprentice in the first place. An EU novel
Darth Maul: Shadow Hunter, which serves as a prequel to TPM encompasses Maul's personality and role in the SW Universe better than anything Disney have done. And he is much more menacing and dangerous in the EU as well. Maul didn't have to get involved in politics and have ambitions of his own, that just wasn't him. And he should've died in TPM (he is considered dead since TPM in the EU/Legends lore, as far as I know). I'm not even starting on the fact that they took Kenobi's well-earned frag away from him by making Maul survive all that. Justice is served now, I suppose, but still. I would say that Maul wasn't overrated for what he was. But Disney hape overblown his premise and made him into something he was never meant to be. So I'm 50/50 with you on that one.