re: Ever seen 405 go up this fast on deadlift?

Honestly I think you are getting to that point where you could experiment with a deadlift every other week. Imo you are getting to the point that building speed matters a lot more

Other weeks I'd work on front squats good morning heavy kettlebells swings or hang cleans etc.

Or if you don't I'd do speed deads or cleans on the weeks I'm not pulling too heavy.