Mirror Shell and Iron Skin - New Secondary Effects?

An idea for alternative secondary effects for these two runes:

Iron Skin

• 5 Armor

After level 9, damage from Critical Strikes is reduced by X%.

X would be a number chosen so the effect is neither overbearingly strong nor too weak. Gated by level to prevent unintentional strength in certain lane match-ups - did you know that 's amplified E and 's single target Q count as critical strikes?

Mirror Shell

+5 MR (+6 MR on PBE)

Take Y% reduced damage from AoE effects if they hit at least one more champion.

For Y, see X above. The restriction for another champion hit is to prevent the effect from being to strong in lane, again.

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Alternatively, these effects are ideas for their own, seperate (and thus more powerful) runes.