User blog comment:Attheendoftheday/Summoner Spell: Barrier Buff?/@comment-24036535-20140805220654/@comment-24184765-20140806002408

I do like the idea of giving Barrier an AR and MR buff, it is what I personally have said that summoner needs to make it viable. but the numbers you’re talking about mean that characters like assassins can become secondary tanks and initiate soaking up even more damage and still being able to assassinat a high priority target.

So I think the number of AR/MR should not exceed roughly 40 at late game and start at 15-20. I say this because it allows champs to have better effective health to tank burst damage but not make squishy high damage targets overly tanky.