LOL 400 towers per player is stupid in the first place, WC3 is only made for 100 units at most per player so I recomend reducing that to 100 towers per player and adittional walls. I would not excede 255 towers which attack every 1-2 seconds per player since modern computers can excede WC3s built settings, DEFINATLY have no towers attacking more than once a second with 400 towers per player.
If you mean 400 towers over 8 players, then that is no worry as long as you follow the wise saying of NO RAPID FIREING TOWERS.