1) I'd need to setup ALL possible devices
I think any solution would need to do this. I don't think there's a way in Vera to get a notification for every variable without explicitly setting up a callback (I might be wrong on this, but I think this is the case). This could probably be automated, but the result would be the same.
2) DM does not log Events
dataMine logs all events into a file called "Notifications" (with a number on the end). The format of this file is a JSON file so it's pretty easy to parse and use. All events are logged - not just events from devices you have configured for dataMine.
3) DM has a MAJOR problem - if there are too many log files it stops working. I hit this issue about once a month with only a few items being tracked then I must go in and manually delete files.
This is not correct - maybe your USB stick has an issue (??) or something else is wrong, however I have thousands of files in my DM directory and have no problems (I log 85 variables right now, so that means 85 files per week). I know of others that are doing similar (and I know of one user who is logging hundreds of variables). USB usage on Vera does have some issues, and you may be hitting against them...
Also, as Garrett says, the latest dataMine update changes the format so there are fewer files in each directory (only 1 file per week).