Probably good for 2 blocks and 6 attack, which is pretty reasonable for a 4-cost ally. The response seems pretty niche, especially in single player play. I can't come up with a whole lot of reasons why playing a Hero action event in the villain phase is superior to just waiting for your turn, though it might let you take out a minion before it activates.
Sendero de guerra
James Proudstar
Aéreo. X-Force.
Dureza.
Respuesta de Héroe: después de que Sendero de guerra defienda contra un ataque, juega desde tu mano un Evento que tenga una capacidad de "Acción de Héroe" (pagando sus costes).
Expensive, probably cappable of handling one extra villain's attack while at full life. And basically is the best partner for Change of Fortune since you will be able to play an Hero Action event on villain's turn, which should be something that does enough damage to kill a minion.
But its very conditional: requires you to play a Protection aspect deck with proactive damaging events... which is better achievable with Hero specific attack events instead; and also requires you to have a defeatable minion on the field and Change of Fortune on the field.
All of these conditions met? You will have a fantastic time. Any of them dont? Then it was an expensive card for 1-2 villain's block.
Sidenote: you could actually use Warpath to block a minion that you want to kill, but that means the villain will hit you instead...