On that, beatmen quest in the footfills the combust spells these guys cast dont seem to let you make a saving throw.
I, unintentionally verified it to myself a few times.
The burning after effect has a save though, just the initial damage doesnt.
There is no saving through for the first part of the spell, only the stop-drop-and-roll part. (http://nwn.wikia.com/wiki/Combust)
Combust doesn't have an initial save.
Er... Combust never allows a saving throw vs the initial damage. That's why it's soo good to flambe halfling rogues ;).