Against which factions is it easier for demons to fight, and against which is it more difficult?

Hmm... after the release of Heroes 6, will you stop playing Heroes 5?

Well, just like people didn't stop playing Heroes 3 after Heroes 4 and Heroes 5 were released (and there are even fans of Heroes 2!), they won't stop playing Heroes 5 – especially since Heroes 6 is still in development.