Which faction is the most interesting to play as, and what strategy do you find most engaging?

Yes, but you have to agree with me, I haven't seen any hero whose skills develop so evenly and with equal priorities. If it's a mage, then their magic skills will develop significantly... Isn't that right?

Yes, but there are many different buildings on the maps that increase characteristics (arenas, towers). Thus, you can increase either attack or defense, or develop them equally. The same applies to strength and knowledge.