I have to correct myself. There is a 3rd niche: using Aeron to protect against the negative effects of the Springvale heroes’ specials. Although in all honesty, the self-defense-debuff of Lepus / Jack isn’t too bad; and if I’m bringing Lady Wooly she’s often my sole healer due to her speed, and she’s +15 so her cleric talent often protects her. And I don’t have Killhare, so no practical experience.
Doesn’t change my answer though. useful, a small niche, but very situational.
another niche for Aeron: he can pre-emptively block things like the Museplheim realm bonus. Pleasantly surprised that he and his flanks were protected from the burn damage