Yeah , I was disappointed to hear this is focusing on prequel area characters too . Although , Dave Filoni is helming the show and he played a large part in bringing a lot of EU characters and concepts back into "canon " . He has also been known to play his cards close to the vest and not revealing things to the public and sometimes his own crew .
I would love to see a series on EU characters too, or a series on any era, rather than just the Prequels. That just seems so limiting.