Aww, how sweet?

I found the poem My Mistress' Eyes very odd. I first thought that the poem was going to discuss love. However, instead of complimenting his mistress, he points out all of her faults. He takes every romantic attribute of a woman and says that his mistress is the opposite. This seemed weird to me. Poetic writing is usually romantic, whether it discusses love or not. I thought it was interesting that Shakespeare would purposefully do the exact opposite. The last couple lines confused me though. I couldn't really tell what he was saying. One of the interpretations I considered was that, even thought she had all these faults, their love was true and heaven-sent.