Lag makes them impossible. 100+ ping and there's no way to safely deal with them, try to shield push them away? they'll attack before they get pushed, leaving their cloud and trapping you while the others move in and attack, cancel your shield for a sec and the cloud gets you, if it's shock you're just dead, no refunds.
Just another example of the developers never having played their own game. Because this is just bs.
Devilites are bad enough and with lag even worse, their shots always hit you even when you're not even close to them. But greavers are basically impossible. Fix it.
Another example? What's the first example? A lot of the GMs do play SK, and OOO don't exactly have a massive archive of games for its GMs to be busy with; they give a fair chunk of their attention directly to SK.
They're not broken or impossible, they're just the hardest mob in the game, especially shock ones.
The only problem here is (and you'll know it if Asul the rager sees this thread) that instead of simply asking for advice, you're goin' on a rant and demanding nerfs. It's lazy, half-assed attitudes like yourself that result in perpetual nerfs and the game being made boringly easy.
Use the search function, or make an advice post, there's threads like this all the time, and all too many of them are QQrs like yourself.
Go read this, go to T1 and look for Fiend floors and practice.
http://forums.spiralknights.com/en/node/39692
Less QQ, more bat-swatting.