Some of the skills the heroes have don't seem to make logical sense, even if the character isn't bugged per se.
For example, Last Defender and Bulwark Angel carry gigantic shields, and yet they don't benefit from the rune stat larger shields. The Goblin Trio have magic bucklers (a type of shield) that heal them, yet they don't benefit either. Some characters create actual shields (Plant Soul, Silent Spirit, Water Wyrm, Groovy Druid) yet don't benefit.
Zombie Squire is one of the most useless characters in the game, and part of the reason why is that he doesn't do any necrotic damage. He's a rotting corpse; obviously he should be doing necrotic damage.
Almost all dragons should do fire damage, yet Snap Dragon's execution skill doesn't, even though flames spurt out of his mouth.
Doppelganger should benefit from all rune stats since he changes into any character he wants to. If he turns into a physical damage character like Bardbarian, he should benefit from armor penetration and life steal.
Shadow of Sven dashes across the screen with his sword aimed at the farthest character, yet he doesn't do piercing damage.
Catapult Knight rains down rocks, both physically and magically, on his opponent's heads, yet he doesn't do bashing damage.
These little tweaks would make a lot of weak characters a lot more viable (Zombie, Snap, Last Defender), and would make a lot more rune stats useful.
Are there any others I missed? I'm just talking common sense tweaks, not something illogical.