Look up posts by 'Alecta' and you'll find information on the resist curve. Off the top of my head I think the break point is around 140-160 in a particular resist.
Don't assume you'll only be eating lures at a high level, only one class can cast those.
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It also depends on your class. I tend to stack a lot more MR on my rogue as I do on my shaman for example, as a melee snared/rooted is worthless but a shaman still can do things.