I still think Sticker Star's version of Bowser is the worst villain in the Mario RPGs. Vanishes after a very brief underwhelming intro, then no presence until the end, only mentioned by other characters and when he finally does appear he's just a generic roaring monster that never utters a word even after he's defeated. Dimentio provided some parallels with M&L's Fawful in his dialogue and had a plan that is slowly made apparent throughout the game. I'd vastly prefer that to "bad guy is bad, he'll try to kill you at the end kill him first" in an RPG series, especially this one that I only got into mainly because of the characters and plots.
I can't comment on what Dimentio's apparently a ripoff of, but there's a lot of things that reuse ideas and that's not inherently a bad thing (TV Tropes is full of examples of recurring tropes in media). These things are common because they work, and in SPM's case it applied these things in a universe where you wouldn't expect it to great effect.