He's large and in charge (and still being painted) but I learned on Tuesday night that the Stormwall is not unkillable, in fact he can be quite the opposite.
You see, having a model this prominent in your force means that every single debuff available to your enemy can be placed on one impossible to hide target.
In one round my poor Stormwall was subject to Gormans Blind Oil, Denegras feat and Parasite spell, and something else debuff related.
It ended up on -6 Def, -7 armour and -2 to all other stats, and having to forgo its movement AND activation.
After all that it still managed to absorb almost all the enemies firepower for 2 rounds only exploding late in the second round of attacks to a pistol wraith.
The lesson is simple, kill them debuffers as soon as you can.