I also noticed this oversight. I find it silly that my magic immune units can't be debuffed but can be blased by fire balls and blizzards for full damage.

Yes either this or allow us a chance to resist dmg spells as if they were curses or whatever.

The only really good way to do this in the XML would be something like:

(CastingUnitSpellMastery / TargetUnitSpellResistance) * SpellDmg

This would amplify the power of the spell if the caster has a higher spell mastery than the target's spell resistance, and vice-versa.

Easy to mod.

However, since you can't use IF or > < statements in the XML calculates, there's not a good way that I've found, without some changes to the base code, to use a straight -x% formula for this kind of resistance as the game currently stands.

I know you're calling for a change, I'm just letting you know what's currently possible without too much code work.

This would make Caster Sovs useless, especially with the incoming XP sharing nerf.

I really hate it when people take an idea that doesn't even specify an effectiveness and say "OMG SO RIGGED" without any idea of how effective it would be beyond their own fantasy. Worse when said in a one sentence post. The dmg reduction could be anything from 1% to 100%.

You could just as easily make the % only do less dmg to creatures/champions with more SR than you have SM. You could make it so you do more dmg to creatures with less SR than your SM.

OP is generic enough for us to fit a lot under it.