I play on a PvP server, so I find fire to be the best of the 3 specs on argus. I save my combustion and trinket proc's in case I get attacked by a horde, (or if I'm in a tight situation) and I do fine. I run with the dragon's breath helm as well so I can take out massive groups of mobs before really feeling a hit in my health.
A lot of people seemed to be surprised at the massive burst fire can pull out of nowhere when they can attack me. (I typically win 75% of fights, and I only die on maybe 5% of them as I can run away with rocket boots, glider, lightforged warframe)