It is based on 11th level not 8th.
(For further confustion, when the 'loths were introduced - later the yugoloths - they had MR ad different levels for different spell levels - each level over 1st having 5% less MR.)
Back to the OP and I would say it depends on what the divination spell is doing. I think for a locate X spell it makes sense to allow MR to apply, but for a see invisible it does not - one acts on the creature, one on the caster.