Where have you been last few years, when Karazhan and Cathedral went into m+ rotation in Legion whole swaths of abiliities were nerfed by up to 90% because they were completely not planned with m+ in mind, they were designed to be dangerous on m0 and when people started doing +20 and above they were absolutely bonkers. Seat of Triumvirate remained a mostly dead key and even m+ enthusiasts could only clear it on a couple of levels less than everything else (post nerfs).
Corruption "balancing" same story, resembles legion lengedaries balancing where sephuz went from the worst trash to bis for some specs. Worst part is now you can cleanse a corruption that is trash only to see it buffed next week and your previous op one nerfed to the ground. "Rofl sorry guys" indeed.