Go to the strategy window and set "group at 15 minutes". Anything else is detrimental right now.
*EDIT: actually, nevermind. Just watched the game and it was ... well... a clown fiest a I suppose. Haven't seen such a weird game so I really dunno what could be wrong (aside from the fact that your guys seemed to group around 17mins instead of 15).
What is really needed is for other strategies to be more effective, or towers to not go down in 5 seconds against a 5-Man-Push.
Right now there's literally no punishment to grouping ASAP and everything to lose if you do not group.