@Detlef Sure, except replace "exploit" with "use a game mechanic that is out of line power-wise compared to others", it's no exploit, simply a 1hr ability that ended up being overtuned, any nerf to SMN should be accompanied by either a nerf to the HELMs themselves or along with new content that will at least somewhat reset the playing field in some way.

Imagine if it were as you say an "exploit" but they chose not to ban anyone, that would just reward all the people who "exploited" and screw over anyone who didn't, that doesn't make much sense to close the door this late in the game, it would've made sense like a week or even a month into it, but now? If it were in any way what is in game terms an exploit, people would be getting banned for it.