Derailleur pull ratio seems wrong

Setting up 1×11 with deore shifter, rear mech and 11-52 cassette.

Issue:
I set up limit screws no issue. I then shifted down, and found sometimes it was shifting two cogs. I tried loosening the cable (clockwise on the barrel adjuster). This works, but when I shift back to the highest gear, the cable is very slack -with the derailer remaining in the highest gear for a few clicks.

It seems that the cable pull per gear is greater than the tension needed to get the derailer to shift one gear. If that makes sense? I can't even get the shifter to click 10 into bottom gear before the chain is on the largest cog- the cable tension gets so high.

Ive tried about of troubleshooting including:
– setting b limit screw as per manual
– tried different chainring sizes (pictured is the smaller one I tried)
– tried with derailer extender since it's a massive cassette
– lubed cable and chain