Do you ever find your throughput lacking when Chi’Ji isn’t up? Or did you feel that way when you were 400-405 ilvl? Were you in 18-19’s at that gear level?
My experience was that caster MW helped me push lots of throughput when I needed it and that was a time (still is I guess) when damage wasn’t the limiting factor to timing keys and instead being able to burst 100k+ HPS when things go wrong to save a wipe or being able to babysit tanks and heal through debuffs on DPS without defensives being used is what kept the group alive and allowed me to time keys.
It could be that I’m just a horrible Fistweaver because the numbers you talk about make it seem far better than I could manage consistently. I found there were times when I had CD’s up that Fistweaving throughput was really high but I also found there were many times where it was horrible.
Granted I’ve been 10-15 ilvls below you but you seem to do really well with damage and healing. If you’re routinely adding ~20k DPS to a key and keeping everyone alive and getting through Tyran Hyrja’s, Tempests, Fenryrs, Azureblades etc, then the Fistweaving build could be much better than I give it credit for, it just hasn’t been my experience. There also have been quite a few nerfs to dungeon mechanics since I’ve played FW.
I’d love to see a breakdown of your healing from the 18 RLP to see what I might be doing so wrong?
Also would like to make it clear that I tend to avg about 15 interrupts per dungeon! This IS HUGE. Maybe the biggest thing you can do is interrupt spells! 
Maybe when they get to 100% I’ll give it a shot!