Been farming this stuff for alts, and have noticed the drop rates vary wildly - which is intended. What perhaps isn't is that drills maintain a 1/50 drop rate at the moment. I'll break it down.
Medusa - common mob - drop rate 75% ish (or 'like candy') - nano only.
Medusas are available in hordes in two places, and drop like crazy. The server lag is likely caused by the sheer amount of nano armour drops. Its also available in nicely high QLs all the way up to 250+.
Borgs - common mob - drop rate 3 % ish (or 'most farmed RK mob, should be low') - all types. Borgs drop everything, but its rare - but as they're the proto-hecks, I've no problem with this. Players are going to be killing them anyhow the armour is just a rare added bonus. Qls they drop is also high - meaning yes, 220's ahoy, whinging lowbies trying to level off them whilst 220's multi-kill everything just for the small chance of high ql drops.
Avians - rare mob (one camp) - drop rate 50% ish (or 'pretty good as they only drop one type') - scary only. Avians are the perfect balance - drop only one type, and the drop rate is ok. e.g. spend the time to search them out, spend some time farming them and you're likely to find the armour you want, if not in a high QL, as mobs are only 160.
Aquuans - ultra-rare mob - nobody knows (or 'not available in the wild really') - ?? Aquuans - don't exist over 90ish, and even then they seem impossible to find. I've even been poking swamp mobs in a vain attempt to see if they're related - they're not.
Drills - rare mob (three small camps) - 5% ish (or 'totally borked') - tank, melee, ranged, nano. Drills - three tiny camps, and they have a terrible drop rate. They also drop nano, which is just insulting when medusas are putting it out like they were on the game. Also only one 210 mob out there, who appears to have forgotten that loot tables were updated - I'm not convinced the DAV island mobs have had their tables updated, I might be wrong: but after camping them four times for no drops, I gave it up.
Questions / suggestions:
Why did drills 'luck out' and get such a wide drop table when they're a) rare b) not available in ultra high qls? Why are they even dropping nano armour?
Why didn't RK get some new spawns of the mobs which just aren't available in the wild? There's plenty of areas totally empty that might have liked some high (200-250) level mobs. Only medusa (210ish) and borgs (200) drop high qls... and they're the most common mobs!?! >.<
If the intention was to have certain mobs only dropping one type (avians, medusa) at a high drop rate, whilst having all dropping from one mob (borgs) at a low level, why did the medium spread get a drop rate nearly as low as borgs?
I'd love it if someone took a look at the drill drops (and took nano out of there already) and sprinkled some high level avians, aquuans (hell, any aquuans) around, and then fixed the DAV drills. Actually, I'd love to see the kinds of numbers for the last three that you get for borgs / medusa, but hey.
p.s.
Top suggestion - I'm pretty sure people would love it if RK missions didn't hard-cap the mob spread by level (e.g. aquuans stop at 140ish, drills at 180, medusa by 190 etc - after that you only get mechdog mobs). If you could tweak the mish spread on chaos to include high level monster mobs (not just the five mentioned) I'm sure this would make a lot of people happy.