Hero attack is added to the attack of every individual unit to determine the attack value that's actually used in combat calculations, so every character class will benefit from a high attack (and defense). Mana is regenerated in real-time on the exploration map, balanced out against any rage that you built up decreasing (if you don't care about all your rage going away between battles then there's no reason not to just wait the 20 seconds or so needed to ensure you start each battle with a full mana pool). Within battle regenerating mana is a bit more difficult- one of the skills in the mage skill tree, Concentration, will allow you to regenerate 2, 4, or 6 mana each round depending on the skill level. One of the spirits of rage has an ability that will allow you to regain some mana. And finally Green Dragons have a unit ability that restores some of your mana while damaging enemies.
