There are 5 different jobs on flame levi, each with its own requirements.
Siege Drivers: Pilot the siege engines, drive 'em around to where ever you're supposed to.
Siege Gunners: Anti air and anti ground gunners. The anti-air can light the oil slicks on fire **this is HUGELY important, it does a TON of damage**. Probably the best spot for those who aren't used to, or don't enjoy vehicle fights.
Demo Drivers: Pilot the demo's, launch pyrite barrels for major damage when Flame Levi is stunned
Demo Gunners: Most unique position, get launched onto Flame Levi's back, probably want to ranged dps and a healer (hunters are a bad choice, though)
Motorbike drivers: 2 jobs: 1) lay oil slicks on the path of the boss, and 2) pick up the parachuted demo-gunners when they get tossed from the back of flame leviathon.
Now, you can find strats elsewhere, but I've made a diagram, the idea being, to show how to properly kite flame levi.
Now, the first panel shows the initial setup. And, in this theoretical, I'm only dealing with when a demo is picked to be chased.
At the intiial aggro, the person being chased heads to the corner opposite where you start. You'll go a tiny bit south once you get there, but thats okay.
In the second one, you can see where the Demo's should have set up, right along the kite path to his NE, at max range of their guns.
If one of them is picked, they go right to the corner, and just wait. This entire time, motor cycles are laying down oil slicks and he's getting burnt to a crisp.
As he's chasing that Demo, the other demo's slide around, behind him, once again moving to max range.
Now, obviously, this isn't perfect, if he gets stunned at a bad time or in a bad place, he'll end up chasing someone on a short side, and catching them pretty good... but, if you can keep a solid kite line, and keep running him over oil slicks, he should die quick.
When he doesn't die quick, its because he's being kited all over timbucktu in a circle because no one moves to the right spots!