Alright then, I word it more simply;
People expect chaos dreadnoughts to be unhinged and more violent.
Whereas SMurfs stick to honour and being goody toe-shoes, chaos is chaos. Someone looking at a dread' that's chomping through people aren't going to think "Bloody hell, he's much more sane than THAT chaos dreadnought!"
It doesn't matter whether fluff says they're not insane.
Chaos are aggressive, violent and murderous.
To say Chaos sections are "enraged" is like saying Nurgle smells a bit funny.
So just call it a Dreadnought :3
I know you're trying to find new names to set them apart, but you really don't need to in that case.
Mankinds first mistake; Questioning why those around him, are dying.