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AMR ranks spell hit higher than spell power, above spell hit of 10% from gear, without any buffs like totem of wrath. So it will sacrifice a bunch of spell power and crit in favor of hit.
Elemental precision grants 6% hit to frost spells (despite the tooltip), so 10% (126) should be the maximum spell hit from gear without any other buffs.
I see there have already been some requests for manually setting the hit cap too, so +1 to that FWIW.