Exactly diffrent generals will play differently, a general with flying units capable of fast movement compared to a general like queen of thorns with slow moving trees and an immobile casting platform. The first (as there is some sort of angel general I'm guessing from the trailer)would be fast crippling attacks, changing attack paths evrey few minutes, slowly pushing the enemy back, and pushing them where they least expect it, queen of thorns would be about holding a point against an onslaught and pushing it back or at the very least halting it for a time. (slow tough trees, immobile while casting, aoe push back is my reasoning for this)
So now onto the debate of assassin vs general, looking at the two generals before, if an assassin tried to push through queen of thorns, it would probably end badly, but if he attacked her out in the open, or she attacked him, he would probably be more likely to win (if the player is smart and the other is not the situation doesn't (well... shouldn't) matter) and on the general with the fast attacking angels, he would probably hit and run the enemy, once they go after him he leaves, only to come back a couple seconds of later, wear him down, and then kill him. (for example, this general is fictitious) Where as if the assassin just just the angel he would be more likely to win.
(situation * hero match up) + skill = game (i.e. a good situation for one hero is bad for another, and either way they need skill)