Pyro PT is definitely beatable if you have the jump on them. You need all the defensive cooldowns and Enure to overcome their insane burst but they are squishy as hell and have no knockback. It helps if they blow a stun after Leap, preferably the four-sec one
But as the long post above says, against a well-played, geared Marauder you will lose every time if you both have all cooldowns available. They have so many tools to ruin Master Strike and without that we can't keep up in terms of damage.