Wrath of God targetting question

[Ironhawk]

So, in my past two games, one of the players has cast Wrath of God. It only seems to kill a handful of units so I basically ignored it. But two times now, the lightning bolts from it have *just happened* to kill the most valuable mage in my capital. The first time I wrote it off to unlucky coincidence, now I am not so sure. Does anyone else have any experience with how this spell targets your units? If it chooses powerful mages/priests over others? Or commanders over troops?

Additionally, if anyone has any clue how to find out which units have been killed instead of the completely useless "3 units were killed this season" message, I would be much obliged.