I was just testing out whether or not I had gotten 4 hits off with my Lionheart Honor Blade charge attack (probably accidentally hit a mini-gremlin or it's too rare and unreproducible)... So I found two Poison Lumbers with a Mender, great right? I can do my testing...
So... thing number one... I noticed that whenever Lumbers were healed and they were walking, they would teleport forwards in the direction they were walking.
Thing number two... for no apparent reason, a Mender started to heal the fully healed lumber as opposed to the one that was about to die (I remedied that with some shieldbumps).
Thing number three... apparently Menders don't like corners and breakable blocks because it stopped healing the lumbers until I shieldbumped the lumbers into the Mender's face.
Thing number four... you can shieldbump an enemy such that the Mender actually misses healing the target
So.... intended behavior?
I don't think menders can miss their targets. If they die before the healing spell is cast, they cast it on themselves, I think. Some interesting and weird behaviour, anyway. Might wanna file some bug reports and/or do video demonstrations?