So I noticed that plasma weapons in this game have ballistic as well as energy damage. Now that would produce a really high total damage output but I think its stops them from being 'pure' energy weapons

So my main concern is with the type of damage they cause itself. How can plasma, which is a higher ionized state of matter, cause physical damage? All it shoots out are green bolts of energy, where does the ballistic damage come from?

If it has mass, which I assume it does. It will cause "impact" damage.

But technically speaking, plasma is a state of energy. So i don't know why physical damage should also apply.

It's a state of matter like liquid, solid or gas. Plasma is super heated gas, though light, gas still has mass to it especially when it's concentrated into a small compacted superheated form.

Ever stick a fork in an electrical outlet? A lot like that

TIP: Use a plasma thrower it does wonderfull damage!!!