Statins are apparently implicated in causing/aggrevating type 2 diabetes (and cataracts - both of which I'm suffering from); this was one of the first things I learned when I was researching diabetes after I was first diagnosed. (And asking my diabetes nurse about this during my first appointment I was told "Oh yes - they're good for you"
...) I actually stopped taking mine last autumn due to concerns over some previously very low cholesterol levels. Shortly after stopping them my glucose levels dropped from highish but stable 6s and 7s to mid 5s and 6s. Unfortunately during the same time period I was also taken off long term corticosteroid eye drops, and these steroids I also discovered can also raise glucose levels, so I believe - but can't be 100% sure - that coming off statins has been beneficial for me both diabetes wise, and in other areas, namely increasingly bad pins and needles in both my arms and hands which has now greatly diminished.
I stopped without my GP's permission, although my ex and short term diabetes doctor at our practice was willing to accept my request to halve the dose a couple of months prior to my deciding to stop taking them. My GP is now aware that I've done so and there was a note on my recent blood test to this effect.
There was a very long ongoing poll about the effects of statins when I first joined the forum in early 2014. It might be worth having a search for as it made for rather worrying reading, although at the time I wasn't aware of any of those effects for me!
Robbity