Well, there are things you can do that wil certainly bring your grip up much faster than your DL. In fact, my grip strength is pretty far out in front of my DL, which would make just training DL and nothing else... well, it would make it de-training for me. Anyway, dead lifting isn't really considered a test of grip strength. Powerlifters aren't deadlifting to improve grip strength, grip strength is necessary for DL's. That was kinda my point. That is where I was drawing my back/curls example from. Lower back strength may be a requirement of heavy curls, but it is not the target of heavy curls, and if your mindset tells you that the way to train your back up is to do more curls at heavier weight... you are right, there is SOME training effect there, however it isn't the target and it is a pretty inneficient way to develop grip strength.

If the only thing you are ever worried about is how much you can put on a bar and hold, then maybe you wouldn't need to train outside that parameter. I compete in strongman, and I put my hands through a lot of work. Heavy farmers, tire flips, stone loads, keg carries, hand over hand rope pulls, axle deadlifts... pretty much everything in strongman starts at the hands. With the exception of something like the yoke walk, I'm drawing a blank as to any events that are truly "grip free." Things like tire flip and stone loads are open hand, finger-tip strength. Deadlift doesn't help that. However, that fingertip strength will translate over to deadlift. In fact, in my experience, just about any OTHER kind of grip training vastly helps your grip on deadlift, while the supporting grip of a standard bar deadlift simply isn't sufficient to help anything else.