The worst part about maulers seen from a shielder's point of view is that you have to react differently to them than you do to most other things. So if you have a guy about to lolstab you with something and a charged-up overhead maul type, you have the choices between getting overhand raped through the shield or lower your shield to dodge or swing and get lolstabbed.
This, however, is not much different from the advantage a 2h axe and a spear type have when working together well. Sure it's fucking annoying. Not even close to nerf-worthy though.
Honestly I think mauler is one of the more difficult classes to play. Takes patience, timing and a very good feel for the length of your own penis weapon as well as that of the enemy.