Using straps on all my back movements has definitely cost me some grip strength, but I think the benefits outweigh the negatives. I'd been using straps for so long I didn't even realize it until I forgot them on a shoulder day and discovered I could barely hang on to 315 long enough to complete a set of shrugs.
I can't remember where I read this, but when you squeeze really hard with your hands, your biceps automatically take over more of the load. It's a physiological thing we have no control over. With straps I can use my hands more like hooks and really focus on hitting my back.
You can always compensate with farmer's walks and wrist curls.