About Elemental Damage

I still haven't quite figured it out, so I'm gonna ask.
Say with a Combuster. It does fire damage right? What I don't know is if it does fire damage on every slash or only on the charge attack.
I'm asking this now because I need to know if investing in Voltedge for PvP is wise. My reasoning is that not many people have shock res. But if the shock damage only comes from a charge attack, I'm not gonna even bother.

Is charge only, as is combuster, elemental damage unrelated, and probably would go in armory.
*edit*
I took ages to phrase my short sentence, and a kind vog guy beat me to it.

actually on the status effect side of things, shock status incurs elemental ticks. The others deal normal damage numbers.

@Negimasonic - Is that so? That's actually helpful.
Though it seems that it will make little difference if I switch from Combuster to Voltedge. The price is gonna be high to make it. Maybe I should invest in some "+charge time" trinkets to make the most use of it.

On that note, it seems that players don't take damage when freeze expires whereas enemies do. Is that supposed to happen?

@Leinhart, not sure what you're planning for (I know you said PVP but still). In PVP voltedge PERHAPS is more useful since shocking on charge will probably make them easier to kill than fire (but ice might make that even easier since you could just freeze them and do another charge to kill). The damage from shock isn't very impressive (the shock effect damage, not talking about the charge attack itself). That and there's still a lot of people running around with vog might make fire less useful. But there has been a rise in things like divine sets, so fire could still be useful.
Either case requires you to spam charges though. Otherwise there's no difference like others have written.
@Sylvanius, probably. If you've ever been frozen by ice cubes dying (or the attacks themselves), you don't take damage from thawing, so yeah I assume they mean for it to be like that for players. Even though that IS odd. I guess they decided freeze was already dangerous enough without that.
There is no "shock," "fire," or "freeze" damage, those are status effects. Elemental is elemental. Combuster does the exact same damage as Voltedge and Glacius. The difference is in the status effects they apply. Combuster applies Fire, Voltedge applies Shock, and Glacius applies Freeze. If you're not going to be using the charge attack, they are interchangable. Now, if you want to use the charge attack, for PvP go with Shock. For PvE, go with whichever is best for the stratum you're facing. Just remember - if you're attacking a Slag Walker (fire zombie), Combuster will do the exact same damage as Glacius. They are all three interchangable with regards to normal attacks.