Using Westside, my deadlift went up without any deadlifting or rack pulling or even goodmornings. Just speed and heavy box squats with bands, and Zerchers with a 100-140 pound sandbag. BUT by squat rose a lot faster than my deadlift. When I started, I deadlifted 375 and squatted 345 and in one year I DLed 410 and squatted 425 and so far have DLed 435 and squatted 445. At some point my squat surpassed my DL.
I used to DL sumo before Westside. Basically I'd max conventional and then move out and I'd be able to get 10 more pounds. I switched to Conventional because basically it was faster but today I might recommend training Sumo fast but lifting Conventional. The more I deadlift one way of the other, the more my body starts not liking it.
I don't currently follow the westside protocol 100% but I will say this: in training I firmly believe that you should go wide as possible on squats wide on DLs. Then come in as close as you want when you max. I can squat more a little closer, and DL more conventional, but close squats and DLs do not make me stronger.
Also a strong grip helps even if you are not losing your grip on a max. I used to always fail from grip. What stopped that was walking with a wheelbarrow with 300-400 pounds in it for 10 trips of 60 yards.
One assistance exercise that does help is a special kind or barbell Zercher which I will do from the rack. I put a 5 foot long sleeve of PVC either 4 or 6 inches in diameter over the barbell.
This thickens the bar and puts the load several inches further out. Then I roll up a towell an put it over my neck so that the 2 ends are hanging in front of me on my chest. Then when I reach under the bar, I reach up and grab the two ends of the towell. This lets me hold pretty much any weight.