The only options for merging contacts are either 1) merge all contacts or 2) merge them one at a time. I have 300+ contacts to evaluate merging and I know that there are at least a few dozen that should not be merged because they are different people (e.g. David Anderson).
The individual merge takes a long time. It has probably taken me an hour to get through 60-75 of them. That makes it almost not worth the time. It would be much easier to be able to toggle "merge" for multiple ones I choose individually and then merge only those.