Are you thinking darkfire maybe? Darkfire is 1d6 +1 every 4 or 5. The wizard one is (or should be) intentionally more powerfull because... well, a wizard cant turn himself into a soloing machine like a cleric can with the spells unmodified. A wizard's flame weapon is a party buff as opposed to how clerics most often cast darkfire on themselves.
Even in the default versions of the spell the wizard spell becomes more powerfull than the cleric at higher levels even though it starts with a lower damage die.
I rather agree that +1 every level up to 10 is probably too strong and stops increasing too soon, but it should progress more quickly than darkfire +1/2 or +1/3.
Even if +1 every 5 is how its currently implemented, my level 8 sorc is still getting the +1 version rather than the +2 which is what he should have now since the spell starts at 1d4+1 when you can first cast it at level 3 or 4 for wiz/sorc.
-TV
