Grieving Mothers spell list at lvl 9 included this little surprise for me:
http://imgur.com/AiRVlKZ
Now Im no expert but I get the feeling that Detonate is not supposed to do 11201 Raw Damage.
Which it does:
http://imgur.com/odHyJUg
...with a graze.
Its also the only nuke spell at that level for her so... she now has one usable spell since thats just silly.
Not a game breaking bug like some of the other ones that Ive managed to avoid with dilligent saving and backtracking, but mildly annoying none the less.
Unless I feel like cheating everything with what I can only assume to be the ingame equivalent of the Godhammer.