First off, I know that Greavers attacks can be interrupted when they're struck, but let me tell you, that's not always EASY TO DO when they're hording you and attacking at different times AND moving around you not staying in a single position. Oh, and lets not forget that cheap, cheap, cheap dust attack they do, seriously make it so they do it on SOME attacks, not ALL, because there have been separate occasions when I had nearly full health then after fighting a horde of Greavers, remember this: I'm actually pretty good at handling Greavers, I have barely any Hp left, this especially qualifies for RUBY GREAVERS, it's not always fun to be doing well then fighting one horde of Greavers and be near death, oh and then after that LOOK another horde of Greavers! Yay! That's always fun.
Why not increase the radius of the Greavers dust attack and then make it so they CAN'T get through shields? Your shield is your best buddy in tight situations, like being gang banged in Arena's, that being said lets set up a scenario: You're in an Arena in the third match and a horde of Mecha's start gang banging you then a Greaver dust attack (Lets pretend this is a Shock Greaver) gets you through your shield that's hopefully still in tact, you're not going to live, sorry pal.
OH, and one more thing, the range of Greavers is misleading, there range is farther than there attack animation is, please fix that because it's highly unfair.
Remember, I'm not bad at the game, so don't say "Oh if you can't those then you suck" or something else like that.
If you use a heavy sword (ex: Sealed sword/Troika lines), it's super easy to swipe at them when they try to mob you. In fact, you WANT them to try to mob you, because that's when DPS with a heavy sword is the best.