Ashes : How do you play with 4 player?
I've had an answer from Isaac Vegas. This game is competitively based on one versus one, for 4 players play, it's better to make 2 1v1 battle, then a 1v1 battle for losers and one for winners.

Based on further play with friends, we discovered that 2v2 is quite balanced in most cases, and 1v1v1 works quite swiftly.

To prevent stalemates, what is advised is taking risks. Forcing others to attack by fragmenting your forces will incite them to strike you BUT, one will react more strongly than the others so it's supposedly the first to react that'll be maimed.