ExRx.net

Well, you may be right in that you can't pull evenly with a mixed grip. Even when I was into PL I would never DL that way in a competition. But I think it is OK if you alternate grips. Straps are fine IF you are doing an overload movements. I'm into OL more than anything else, so if I'm going over my maximum clean poundage off the floor for pulls, I won't hesitate to use straps. Another thing I do is to use a hook grip (two fingers over the thumb crush). This is a staple. It hurts, but over time, you'll get over it.
Tim