The deadlift is something that tends to be kind of “peaky” or inconsistant for me. Also, Dan John talked about “maxes” and “max maxes” and so forth in his article and I think those concepts are especially applicable to the deadlift.
The first time I pulled 475 was after a 12-week or so program of intense training and very much designed around improving my deadlift, even though I wasn’t doing any heavy deads at all. After I hit that max, I could barely hit 455 (and sometimes not even) for a couple of months after that. So that was definitly a “max max” for me.
I think, for me at least, that the deadlift is built by not deadlifting. Of course, I tend to have a good build for deadlifting (long and lanky) and, aside from using too much back, the technique for the lift has always come pretty easy for me. So I’ve always had more success by not deadlifting, and strengthening the hell out of my glutes and hams.
Also, when planning my ME lifts, I tend to like to alternate between lifts that will be over and under my deadlift. What I mean by this is doing something like:
Box sqat(under)
Trap-bar dead (over)
Front squat (under)
Rack pull (over)
I’ve found that has been good for building the deadlift, although my squat has not made a much progress using that method, although that could be technique related.
So I would say, don’t worry about the stalled progress, back off for a little while and focus on your squat, and then after maybe 8 weeks or so of that, go back to focusing on the deadlift, look at your weak links and improve them and see if you can break into the 525-545 territory.
At least, that’s what I would do, you might have totally different training philosphies or things that work different for you, so take my advice with a grain of salt.