I think that Sienna “Battle Wizard” class is not so useful as other Sienna classes. That “fire trail” is nice, but you find yourself (quite often) either in deep-penetrating enemy lines and getting your face tested by enemy weapons, or missing the “flow of the enemy wave” and wasting the special ability potential.
Compared to other abilities - “homing missile with low CD” and “burn’them’all’ALL”, this seems kinda useless for me.
So my suggestion is: maybe you could change that “Battle Wizard” active skill to somewhat reminding the “charge” skills on Kruber/Kerillian/Viktor? Like Sienna gets this “arrow on the ground” when using the specical ability, and then releasing a fire wall at this path that deals a fire damage?