[thejeff]

I'd prefer, though it is a little harder to justify, that spells that produce an immediate change on units (bless, luck, Protection, etc including the battlefield wide ones) leave the effects in place when the mage dies or leaves, while spells that have an ongoing effect (MoD, Storm, Wrathful skies, etc) stop with the mages death or retreat.

Which is, I believe, how it currently works when a mage is killed. That it doesn't happen when he retreats is the bug.