Very little of the actual event has been able to be done by level 30+ characters.
I believe Kathwynn's complaint is more that if you're not somebody who plays at Legendary levels, then this event doesn't really provide any benefit, and makes playing the rest of the game harder.
To be fair, this is a valid criticism. The fairly powerful event champions can be difficult for casual players to work around - even my perma-Legendary character is finding standard questing somewhat more difficult with them hanging around - and levelling a character to 30 is a pretty strenuous affair.
This said, given the number of people posting locations to this thread who are genuinely enjoying the event even at heroic levels, I can't help but find the standpoint of "this event is terrible and SSG should never do it again" something of a depressing one. There were improvements that could have been made, I will grant. But the fact that SSG are prepared to try something new like this is overall a good thing, even if the event itself isn't for everyone.