I’d actually suggest almost an FSL/SSL approach to Kroc rows. I’ve been doing that recently and it seems to work nicely. I usually do just one all-out set of Kroc rows, but work my way up to it.
Now, after the all-out set I drop to my last work up weight and hit however many reps (in a couple of sets usually) I need to get 50 total reps.
Generally for me this means my actual set at 100 lbs, where I shoot for a rep PR, and then a couple of sets at 80 lbs to get 50 total reps.
I’d also play with having a day where your shrugs are heavy and a day where they are light. Try wrapping a thick towel around the bar on the light day and get at least 20 reps per set.
I’m glad it’s worked so well for you. I’m finding the exact same thing.