Hellectic the biggest plus of the Stormwall is survivability. As opposed to killing one heavy most opponents need a lot of resources to take one down. This means it gets to keep operating, where if you have two heavies and one goes down then you suffer half your attacks.
However it's next biggest plus is the ability to shoot out of combat, meaning you can always provide a threat and always do something. That may be the MK's downfall when I get around to using him but to be honest I am not sure it will as I don't use Troll beasts for versatility.