Anyone who wants a taste of the supposedly nerfed Fiends should go into the undead arena in the depths of the latest gate. Every single spawn that normally pops out a mecha knight pops out a Greaver instead. 12+ at once. And they all aggro all at once. And there's Silkwings to back them up. So yeah, stop complaining. I got rocked so hard, I'm physically sore.
*sob* You're so bad at balancing games, OOO.
Greavers were actually buffed as they are now elite class monsters. What you experienced was the end challenge of an arena in the lower levels of the Clockworks, one of the toughest areas of the game.
It's also worth pointing out that arenas are not designed to be fully completed by every player. Each of the first two battle rooms follow with an exit. The second and third battle rooms are optional challenges with the latter designed to be a battle of considerable difficulty.