Have you tried heavy one week and light (60% of max) the next, took me from 90k with a 170kg max to 103kg and 217.5kg max, trap bar deads as well
Yeah I need to do more volume and variations....like I only decided this week I was going to try to lift heavier with my main lifts. Also my technique still isn't great but I do know what good technique is having done some uni level sports science stuff.
I think today I had a 180 in me; I've been avoiding 1 rep maxes and actually looking to actively avoid putting on weight - I've only recently come off a high fat diet after going hard-core keto for some months to lose weight. I had a goal of doing 15 pull ups with no kips hence the motivation to lose weight; a goal I passed well and truly some months ago. I'm 5'7" and was 88kg and was just too fat, and ketoed my way down to about 75 kg. The upside on actually improving lifts is pretty capped if you are losing weight, so I didn't really try, but just in the last fortnight decided to get back on the carbs so I can look forward to now improving my main lifts.
Before I would be lucky to have two bench press/press days every 8 - 10 days, and one of those was a high rep day, clearly I was always going to struggle improving my bench, for example, in such a scenario, but moving forward am aiming to improve my main lifts as I said now I'm sanguine about putting on weight. This means more volume and like you say, heavier and lighter days, within a smaller time-frame.
Having said all that, farmers walks really helped me re: DL, even while I was losing weight. Its like forced base work, I really rate it. I also don't do any iso exercises so plate carries are awesome for an arm workout without having to do pretty backward types of exercises like tricep isos or whatever. Both are also excellent for core/legs/back etc.