The head-bobbing is uneven, he goes down more on one leg than the other, which makes his run look like a weird kind of gallop instead of running.
The fire also reads badly - It's just noise on his head. Maybe try to create more forms in the flames, so that it's a few licks of fire instead? Also, possibly add some particles from the head that trails after him. If you watch clips of fire, like
https://www.youtube.com/watch?v=yGbodsAV03M, you'll see that fire moves in clumps, and once they separate from the main fire, they live on for a bit. Try to get that sort of "life" into your animation!