The intent seems to be to make CC less powerful because, at least at lower levels, no one really has any way to counter once it lands (e.g., very little if any purge or det). However, for 5mans, tank groups were already strong, and now they're even stronger at the higher levels as they all have det9 by then, resulting in the longest duration mezzes having almost no duration at all. This seems like a bad aspect of the change.
On top of that, though, there's the impact for fights between caster groups where det is not at play. In this case, you would think CC would be weakened, but it it's just as effective. The reduced CC duration means a reduced immunity, also. It's not at all unusual to find yourself getting mezzed again shortly after being mezzed. The only way to counteract this for casters is to use purge, but when immunity is so short, purge is not all that helpful.
I would suggest making CC work as it usually does if we have this event again. Sure, it will be really powerful at low levels, but those last for such a short amount of time. Meanwhile, at the higher levels, it's just really out of whack.
On top of that, though, there's the impact for fights between caster groups where det is not at play. In this case, you would think CC would be weakened, but it it's just as effective. The reduced CC duration means a reduced immunity, also. It's not at all unusual to find yourself getting mezzed again shortly after being mezzed. The only way to counteract this for casters is to use purge, but when immunity is so short, purge is not all that helpful.
I would suggest making CC work as it usually does if we have this event again. Sure, it will be really powerful at low levels, but those last for such a short amount of time. Meanwhile, at the higher levels, it's just really out of whack.