What is the extent of the validation of the EDH / Commander logic?

Curious as I have valid deck according to EDH that contains at least one banned card from EDH.

Hello inzeos,

The EDH validation is pretty dumb right now, it only checks that you have 100 cards. EDH in general needs a little bit of love, we'll have a look at better validation, displaying the general more prominently and other nice things in the near future.

Are any of the validation logic checks looking at ban lists? Keep finding myself with banned cards in my EDH decks :0

Nope, right now there are no checks for the banned cards.