Thanks so much for getting back to me so promptly. I have had a busy afternoon and have now changed my enchants to reflect a much stronger emphasis on mastery.
I then signed up for several LFRs and was able to consistently average 50k HPS on boss fights (although I noticed this did vary depending on whether there was a disc priest in the raid)
I did find however that I went oom on a few occasions. Mastery was sitting at around 110% so I’ve tried to replace some of my pieces with more spirit which has helped push me to 1800 spirit which seems more comfortable. Mastery is sitting a little lower now at 103% but that doesn’t seem too bad.
I will definitely try and log some game time in HFC for ppl to feed back on. And will definitely try and hunt down that trinket!