You might be on to something there, Sadrik. Let's stick with 1d8, since that's what divine spells use, but use the base amount + 1d8/2 levels, +1/caster level, with the standard cap (CLW at L5, CMW at L10, CSW at L15, and CCW at L20. So, with CLW, we get...
L1: 1d8+1 (same as now)
L3: 2d8+3...