Oda has managed to keep a series as long and intricate as One Piece the most consistently awesome manga on the planet. Compare the dungpile Naruto has devolved into, and you realise he sure as hell does not "suck".
Being a character that steals the talents of others is a perfect move in terms of making Blackbeard the ultimate foe of Luffy, a person who manages to befriend and thus be willingly given aid from others.
Brilliant move from Oda, as it also means that Blackbeard can justifiably be an unstoppable wrecking machine in a world as powerful as that of One Piece.