Imps will indeed mine gems only for a while before they pick up other jobs. I've made no changes to this behavior. What I did change is that in FX imps would mine all gold before they would start to mine gems, in 0.4.6U imps give gems the same priority they do gold. You said 'especially', implying there is more strange behavior. Could you elaborate?
I've not made any changes to Kari-Mar, but looking into it now, and the Keeper will try to destroy you, getting himself killed. I've made a small change to the map to prevent this: 82KariMar.zip.
Try this one.
If nobody has any objections to the modification, I'll include in when I make a new version.