Imho it's quite evident that the demomen aren't the cause of the disconnects. I suspect another change made at that time, maybe the reserved slots or more likely the bombfrog. The disconnects happen very often when the countdown is at 1, ie when the player is about to explode. Personally I think the bomb frog is very OP anyway, you can blow up a whole team and easily cap points, especially on Attack/Defend maps with only 2 points. All you have to do is run in the general direction...
Please do something, I'm tired of the restarts, of 2Fort and Dustbowl and I really miss the Demo.