The spell, gas explosion, appears to be dealing 1d4 damage per level rather than 1d6.
While the description conflictingly says it does 1d4 damage/level to a maximum of 10d6, I assumed the 1d4 was a typo as it is quite underwhelming compared to spells of a similar calibre, e.g frost blast and ice storm.
I can't really remember what was the original intention, but willing to go with that, sure. Fixed for next reset.