Is there a penalty to fighting weaker armies?

[Sir Whiskers]

Originally Posted by IntelCoreDuo

But how about the hero? Should I reduce the number of stacks or units to gain more XP and level quicker, or do I get a fixed amount of XP from each battle, ignoring bonuses etc?

As stated above, Hero XP is determined solely by the strength of the enemy stack, with certain bonuses for elements such as an enemy hero. The size of your army has no impact on the amount of XP your hero gains from winning the fight.

While I often boost my dragon's XP by bringing in smaller armies (assuming I can still win the fight), my experience has been that it's not necessary to obsess over this. If you defeat most stacks in the game (approx. 300 fights, IIRC), your dragon will come close to or reach the max level of 60. The primary advantage of boosting the dragon early is - if you have sufficient rage - you'll have access to more powerful abilities in the mid-game, which can be helpful. The primary disadvantage of raising your dragon's level too quickly is that you may end up with abilities for which you have insufficient rage.