One solution would be to give hammer spec zerkers the ability to change offhand damage type to crush. In the same way that Shadowblades can change their damage type.
Put it in the hammer spec line for zerker.

What do you guys think?

if you debuff crush resist, it doesn't help offhand. if you debuff slash resist, it doesn't help mainhand. berserker is the only light tank with that issue. How could one fix that? using both resist debuffs at once and hoping they both go off while forgoing other procs is not a good idea ^^ maybe in...