The biggest problem with Biden is that he is so 'far out there' now that he is simply unable to read a script or a teleprompter correctly. He gets confused halfway through a sentence and then tries to 'improvise'. Biden's improvisation when he loses track are always confused, muddled, and hilariously sad.
The DNC plan remains the same. It is more than clear at this point that they are using Biden as a 'placeholder' to sabotage Sanders. Once Sanders drops, the DNC will either replace Biden outright "for health reasons" or they will assign a VP to Biden who will essentially take his place in the race. Biden himself has said that whomever his VP pick is must be able to 'be the President' on day one. This tells me that if he by some miracle manages to win, he will resign almost immediately. They are signalling clearly what the plan is.
But nobody has ever accused a Democrat voter of having intelligence.