Yeah, it's not hard to duo Uninvited Guests; I do it every week with MNK + WHM. You can grab some Rivernewort along the way for an easy exp scroll too, which is a nice bonus. Farming scales is the only annoying part.
I've never seen an assault breastplate drop, but I'll keep an eye out for one. Some of the other rewards are nice too. I got a siren hair from it a few weeks ago. ^_^
Yeah the breastplate itself is pretty rare, I've only ever seen it on one person, but it's not exactly commonly worn gear, its uses are pretty limited but it's great for what those uses are.
The hassle of farming scales is why I thought it would be a nuissance to do.
So in terms of doing the actual fight, how 'hard' are these Mammets? Easily solo'd or easily duo'd?
Easily duo'd. Not sure how others do it, but my friend goes mnk/nin and I go whm/blm. He 2hrs the mammet, and I enfeeble and heal. Our record is 1:15 to finish it, but it gets slower if the mammet uses its stun move or uses transmogrify (physical damage gets absorbed and heals the mammet).