Well, the planning mostly happens outside the dungeon, but he has a point. CC is used heavily in M+ above around and above 20. Especially on Fortified weeks where a caster in the back might just destroy your group. There is a level when even a great tank will be overwhelmed by the sheer amount of incoming damage.
It is also absolutely necessary to deal with the Hypno-Bat of Zulgamux of the Shrouded affix. If you let that shit go through uninterupted someone dies, maybe it is even a wipe.
CC and all kinds of Utility are of incredible worth in M+, especially the premium ones like Interrupts, 60 sec CC that can be applied to all subtypes (and reduce aggro range ideally) and of course Combat rezzes.
Unfortunately even the Devs do not understand this. There is no other way to explain that Priest Dev posting about an Interrupt not being necessary
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Nah, that really doesn't work at some point anymore. Granted it takes a lot to threaten a good Tank with a good healer behind them these days, but north of 20s that does happen.