Dartanis

I had what I believe to be the same "periodic microstutter" bug that you are describing. The game pretty concistently stuttered/lagged once every 10 or so secconds. What fixed it for me was updating to the latest Nvidia Drivers. No amount of tampering with graphics settings, setting them to the highest possible or the lowest possible values did anything to the stuttering so I figured it had to be a driver mismatch of some kinda AND my Drivers were well over 6 months old. If that doesnt work I did remember POE1 having some weird stutter on some computers that went away by disabling extra wireless/bluetooth networks that you may have, I happened to have one and I disabled it too while the drivers were installing but I doubt that was the fix. Mentioning it anyway just in case.

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.