Area is listed as 5' across by 30' high, range 30'.
This seems like a large area at first glance, but it really comes down to a single target doesn't it? (Assuming you can't line up one or more flying targets, which seems unlikely but not impossible.)
Unless I'm reading it wrong - a 5' width is a single square, not 4 squares (a 5'square could cover the center of 4 map squares) or 9 squares (with a 5' radius effect.)
The potential for setting your roof aflame makes this an annoying attack considering its the most potent offensive ability at low levels.