Siege of Boralus didn't teach them anything. Strats like this is absolutely ridiculous, and it should obviously be fixed that they cast explosion while cycloned.
Something about this already got hotfixed https://wow.tools/dbc/hotfixes.php?search=pushid:63486
You also don’t have to sit there and channel Control Undead constantly in order to control it and use a Limited list of its abilities that you also need to manually activate any time you want to use it. Nor do you have to stop that channel any time you want to move or cast any of you own abilities while having full aggro on that mob, needing it to be immediately taunted or you instantly die, nor do you have to deal with healing through it’s damage on people throughout the majority of the instance during the time that you can’t channel the control spell. You just click and forget and the controlled creature does stuff on its own.
The worst part isn't even the upcoming nerfs, it's the fact that now Blizzard knows this mechanic is too hard for them to 'balance' so they'll avoid it in the future and thus M+ further stagnates into a sterilized wasteland.