Diddy may have the annoying bananas... but... they can be caught, swatted, dodged, eaten, power shielded, and quite a few other things and made completely inneffective or turned against Diddy. Characters that remain airborn shouldn't have a single problem with them either. The only people that truly should find them problematic are people that roll a lot. Hell they don't even bother Sonic as he can just spin dash right over them with no effect. Also if Diddy can't catch you near the stage edge or offstage he's not going to be KOing you at any decent percentage easily if you know how to DI.
My Creations in Modnation Racers! Check zhem!
http://community.modnation.com/en-us/players/IvoYaridovich/creations