As for some constructive feedback: I think there needs to be more to the defense stat somewhow. At the moment, it is kind of a no-brainer to just go for health instead (unless I missed some mechanic regarding attacking).
Of course, more variation to the characters upgrade trees would also be cool; but I guess you guys had that in mind with the extra skills that were not yet available. A wizardy character would be cool too :)
Maybe expanding on the chess movement idea would also be cool. I wonder if some mechanic like in the one from board game Ontitama can work where the movements / actions are determined by cards which rotate between you and your opponent.
One last one: the attack animations can be made more exciting. I am guessing though that this was just due to lack of time.