Lava elemental was a no-show until I started killing clockworks. Killing the clockworks does give a negative hit to factions:
- Miners Guild 628
- King AkAnon
- Gem Choppers
- Solusek Mining Co
- Merchants of AkAnon
My personal opinion is that it is better to camp the blazing elementals instead unless you're going for the hunter achievements. No faction hit for them, but it will take longer. They are easily AFK-camped if you are of sufficient level that the mobs are trivial to you.