Most people are cowards that will run away from these players. 2-3 players can easily take a tincan mauler with no problem. The problem is if the mauler is smart enough to get support from his team: shielders blocking other incoming attackers, pikers stunstabbing his intended victim, etc
yeah they are not too difficult to beat 1 v 1 you can just spam them with most weapons the maul is so slow they won't be able to get in any attacks let alone an overhead.
If they are part of a well disciplined squad they can be killer, but so can a lot of weapons if their strengths are being supported while their weakness are being protected and you will probably be slaughtered by 3-4 dudes working well together no matter what. If you have your own crew to counter them then you can check the mauler with your own spears, or set a fast weapon on him to stun him while your guys watch his back when his buddies try and relieve him.
Maul is a very aggressive weapon that gets a lot of people by intimidation but it's also an all or nothing one with plenty of weaknesses.
