This is actually wrong. I used to play ladder games many times when connected via gproxy. And saw no more or less d/c then when using 'normal' gateway. 2v2 aswell. And being host or client didn't matter either.
Only thing that with gproxy didn't work is creating normal custom game (it would freeze and crash wc3).
btw too bad that hostbot solution isn't implemented yet... selfish w3arena