yep happens to me too.
I lag when more than 6 ppl are in the game. It happens when other ppl lag a bit, they cause me to spike.
Reason is probably that i use cable. You need high speed to not lag when there are a lot of ppl.
It ****** me off, because most games have more than 6 players, and you get more experience and gold in games that have more ppl in them.
My friend lvls so fast in 14 player games, while i get almost no exp in 6 player games llol