A bit unrelated but you know what could be a good tactic for an attack like this?
Just mindlessly zergrushing from attacker spawn and into defenders. I mean, they have WAY more troops than defenders so why would they try to cap spawn/camp hill or whatever? Then there would ALWAYS be people to defend spawn (because of all the respawners) and a constant (although depending on the defenders) decrease in the defenders tickets.
Of course I wouldn't use this tactic often, but when you have way more troops than the opponent, attacking mostly with mercs/randomers and fighting on a server on another continent then this might be the best solution.