I've been 1hit killed in the Osiris B by hgauss several times now, from what I'm sure was full/nearly full health.
The AC/UAC20 splash damage really is ridiculous. Anecdotal I know, but when I get an MKII B, especially on marshes, most assaults die to me with - blown out cockpit, deep orange ct, medium to deep orange rt/lt, and often leg/arm damage. This post provides no numbers, sure, but I'm a ct shooter, so try to imagine the kind of carnage those UAC20's are doing to the ct, and all surrounding parts (cockpit, rt, lt, and legs/arms if you're a bit offcentre, not to mention the kill bonus you will frequently get from destroying the cockpit and killing the pilot via ct splash damage).
The new ssrm reload time makes those weapons very formidable compared to before, but I'm sure the AC/UAC20 just plain outdamages them due to the almost stupid amount of splash damage they generate.
Accordingly, they generate a large amount of income, even if you don't get the kill, because you've dealt so much damage across the mech, there isn't really much left for the kill-stealer to destroy.