Good points, Eric.

While there are many types of grip strength, each with their own methods of training, I would suggest that the most valuable for deadlifting would be thick bar holds, or even deadlifting on a thick bar.

It is easy to get out of hand with grip training. Myself, I certainly do a lot of pulling in a week. I do Olympic lifts twice a week, Monday and Thursday, deadlift Tuesday, do some grip specific training Wednesday (pretty low volume), then Saturday is event work (which again is typically pretty low volume). But what I find is that the normal bar supporting grip is truly not close to my full grip strength. So, pulling even close to my DL max isn't taxing on grip at all. Cleans/snatches are stressful in their own way, but not really when it comes to supporting grip. Event work is typically pretty brutal. Lots of heavy work with thick barbells (2-3"), stones, farmers walks (which is far more taxing due to the weight used and the constant jarring as you step. It isn't just holding onto a bar, it is more than that), tire flipping, hand over hand pulls on a 2" rope, etc.

I would say that something as simple as using thick handled DB's for one arm rows http://www.tylergrip.com/ would go a long way towards increasing your supporting grip beyond "adequate." You could also use the Tyler grips for something like shrugs or suitcase deads. Your grip will fail at a much lighter weight with a thick grip, so the total effect on your body as a whole should be pretty light. So something like these exercises could very easily be used as a good supporting lift in a WSBB setup on your DE/RE squat day.