The Hearthguard Berzerkers are the elite version of the Vulkite Berzerkers. They’re tougher in smaller numbers than an equal number of Vulkites if a hero is nearby. I chose to give mine the poleaxes for some mortal wound action.
Ten models seems to be the sweet spot for a smaller unit size. Any bigger and the points discount for the full 30 models starts to look tempting. Smaller and they won’t live long enough to be effective.
Paintwise they’re very similar to the Vulkites. I let the poleaxes be the distinguishing characteristic, rather than via the paint scheme.