He has really good growths but a few negative stat caps (that is, his stat cap in a given class is less than what it should be). He's awful at the start, amazing for the rest of the game, and then "falls off" only if you care about min/maxing.
Also, I don't think he has amazing class options but that's just me :x
Yes. His growth rates ensure that he will be one of your best characters from the mid-game forward if you stick with him. It's tough for awhile but just try pairing him with a strong unit and you'll get there eventually.
Donnel even as a level 15 mercenary destroys promoted enemies.
Donnel has hit level 20 as a Hero, I could reclass him to a Villager, but I've met literally all of the stat caps for that class and I don't want to waste ten level ups. Is there any class I should reclass him into?
He could be a Warrior, a Bow Knight or another Hero!
Yes yes yes.
+20% to his growth rates in every stat makes him a god.
Wow, OK then! Thanks for the advice.