[Agema]

My idea of what makes a bad hero are the likes of Farbaute the Einhere (Vanheim), or Bernlad the Green Knight (Man). They essentially present you with a slightly boosted basic trooptype. Sure, you can theoretically equip them to usefulness, but you'd be far better off spending a few more gems summoning a decent thug chassis (arguably you could be spending less on a summon, as with a sturdier unit like a Banelord you wouldn't need to use as many gems to compensate for so many weaknesses.)

There are some non-magical heroes that are useful outside the frontline. A hero with, say, the Standard ability is useful to keep your units' morale up, not necessarily fighting themselves. Some, like for instance Sporsnjall (Jotunheim), summon units, and in his case both he and his somewhat feeble summons are also stealthy. In some extremely niche uses, there's some Man heroine (Rhiannon?) with a Patrol bonus. None of these guys will put a smile on your face if they turn up, but at least they have some reasonable functionality.