It's difficult, yeah, but Normal isn't as impossible as people keep saying. It's strongly recommended that you play it on Easy first, so you figure out the strategy to the game (okay, not so much strategy as spamming). Tip of the day: Spam your units as much as possible. You want to keep your guys on the opponents field, that way you can build up rep (it builds even if your guys are dieing, as long as it's on the opp's field) and in turn build up your money. Then don't forget to upgrade your units, but only when you have enough cash to spare without making yourself too vulnerable. So long as you can keep them off of your field, you will win. Just stick with your most powerful units and use your hero smartly, and don't let him die. Also, USE YOUR SPELLS. Those things can turn the tide so ridiculously fast and earn you tons of money. Beat Normal 19:33, still didn't get the dragons though. Got close with about 115k XP, but I tossed out too many wargs and a shadow demon (which absolutely destroys) and the enemy fortress crumbled.
All in all, pretty good game, but the fortress upgrades feel pretty useless since the enemy was never really close enough for them to matter. It feels rather cheap with just how many units the enemy can pump out in normal, and how fast the enemy hero comes up and somehow is two levels higher than my hero who has been out longer. Got a bit tedious after a while, with no real strategy other than spam your strongest and use your spells when there are too many enemies.