Relative to the implementation, put a field of each damage type to the encounter table, inestead of doing complex manouvers to a single field..
I'm not sure I follow this bit, or you may be making assumptions about how damage works that aren't true. Currently foes have attack and defense power, just like heroes. So I don't set a damage range per foe, the calculations just work out based on relative power, plus some RNG. So while I guess I could split the attack powers between physical and elemental, I don't know that the numbers I'd have to work with would be very intuitive. (In other words, halving the power doesn't necessarily halve the damage.) I'd be far more likely to just add a percentage for how much is elemental, but then I've gotta adjust for resistance, damage reduction, and all kinds of stuff, all in fractional amounts.