Edit: For context, I started capped for samples so I had 250 rares when the content dropped. I'm getting 15+ Rares from difficulty 5s solo and 20+ from difficulty 7s grouped. Probably averaging 20+ Rares per hour solo, 30+ Rares per hour grouped. I'd guess I've played about 12-15 hours since Thursday, a mix of solo and grouped, and I've pulled in a little over 350 Rares in that time.

I'm at 22/24 upgrades for my destroyer so far, and here's what's been working for me:

• The higher the difficulty, the higher the number of rares on the map (difficulty 4 minimum for rares of course). I do the highest level I can, as long as I can reliably extract from missions of that difficulty. If my friend group is on that means 7s, or maybe 8s if we're feeling spicy. I dial it back to a 5 if I'm solo, as that's the highest solo difficulty that feels comfortable to me. I only get to keep the samples I extract with, so I don't think it's worth trying to push a higher level difficulty for 2-4 extra rare spawns if there's a significant increase in the chance that someone with samples will fail to extract.
• I don't farm samples with randoms. The kind of players you'll find are such a mixed bag, it doesn't feel worth it getting more people to try to push higher level content with more rare spawns. Maybe that makes me an elitist jerk, but... so be it.
• For the minor bases marked on the map, I destroy as many as I can in the time available and then make sure to loot those bases for samples. On difficulty 5+, most bases have at least one rare sample. At this point I'd guesstimate I've got at least 75% of the rare spawn locations memorized for each base map tile. Taking down bases needs to be quick, I don't want to get bogged down fighting enemies. For this reason I find bots far preferable for rare sample farming. One well-placed Eagle Strike will wipe a light or medium bot base, an Orbital Laser plus an Eagle Strike will do most of the work on a heavy base. I find it's a good time investment to get situated so the initial Eagle Strike has the right angle to wipe the base, even if that means an extra 30 seconds of sneaking. That time investment pays off when the base goes down in seconds.
• I'm really diligent about scouring the map. On difficulty 5+, I think every POI gets a static spawn. With the Nuclear Radar upgrade those spawns will be visible on the map before the POI's question mark appears on your compass. I use those static spawns to track down POIs I might otherwise miss. I don't beeline from objective to objective, I meander a little bit through "empty" areas of the map and watch the radar for spawns at POIs. If the Radar Tower spawns on my map, lucky day! I'll prioritize that objective when available so I can see all the POIs and plan the most sensible route through the map.
• I fully clear each POI I find. The map icon for a POI changes from a little jewel icon to a (geometric, non-gem) diamond icon when all samples have been found. Certain POIs don't have any samples but may contain a datapad or other readable lore item. These are typically hole-in-the-ground type POIs like caches or sometimes graves. For these you may need to interact with the lore object to trigger the change in map icon. I use the map icon change to keep track of which POIs have been cleared and which I need to revisit.
• In terms of currently available planets to farm on, I find Penta in the Lacaille sector is fantastic. The weather effect is Thick Fog, which does seem to significantly affect aggro radius. Makes it real easy to dodge enemy patrols, and I don't find the fog hinders my farming efforts at all since I'm primarily using the radar to find the POIs. Martale in the Andromeda sector would be another good choice, if you'd prefer clear visibility. I avoid any map effect that would slow me down. Fire tornadoes, acid rain, blizzards, tremors, etc. would all hinder my farming activities.

In case it's relevant, here are the solo and team loadouts I've been using vs. bots the past few days:

• All situations:
  • Armor: FS-38 Eradicator. Comes from the superstore and costs super-credits, but absolutely worth it. The 50% resistance to explosive damage has saved me so many times vs. bots. And it's light armor so I can sprint around the map more to find POIs faster.
  • Primary: JAR-5 Dominator. It's the closest thing available to the pre-nerf Slugger, particularly in the level of stagger. I find this really mandatory vs. bots, particularly Devastators. They're a lot less threatening when they're constantly staggered. Also one-shots chaff bots with a clean hit. For many POIs I can take down all the weenies before the Devastators can turn toward me (no weenies means no flares), at which point I switch to a Devastator to get the stagger going. If there are multiple Devastators I make sure I'm in cover and shoulder-peek the rightmost target to take it down safely.
  • Stratagem 1: Orbital Laser. It gets three uses, so I try to plan out where I'm going to use them. Generally I'll use a laser charge on the one heavy base on the map, one on a large major objective, and I try to save one use for extract. No other Orbital does as much work with as much reliability.
  • Stratagem 2: Eagle Strike. Wipes patrols and bases, destroys factories, gets three uses per Eagle Rearm. If I'm traversing an area of the map with no bases I make sure to check my Eagle Strike count, and I'll trigger an early rearm if I've got less than 3 uses available. Better to have them for a bunch of quick base takes than use them on dinky POIs and then have a harder time at bases because Eagle Strike is on a rearm cooldown.
• When solo:
  • Secondary: P-19 Redeemer, configured for semi-auto. Good enough to take out chaff bots if the primary runs out of ammo. Also really useful for dealing with jetpack bots. Sprint away when they try to jump on you, they'll land where you were when they started the jump. Hipfire the Redeemer to shoot behind you while running away. Minimizes the chance that you'll die to a jetpack explosion.
  • Grenade: Impact grenades. Mostly for taking down walkers.
  • Stratagem 3: Personal Shield. When I'm solo, I'll be taking all the fire. Having the Personal Shield mitigates a lot of extra chip damage. Also bot mines won't kill me with the shield up and my explosive resist armor on, so that's nice.
  • Stratagem 4: Quasar. One-shots bot factories from the right angle, one-shots dropships if you hit 'em in an engine, one-shots gunships. For tanks or hulks you'll need to kite a bit and use cover to line up multiple shots. Takes extra time, but it's pretty safe. Killing dropships may not reliably kill all the bots on board but it will at least damage some, so still worth IMO.
  • Booster: Sprint, all day erry day. Gonna be running a lot, need that sprint buff.
• When grouped:
  • Secondary: Grenade Pistol or Redeemer. I go back and forth on this one. I'm trying out the Grenade Pistol because I really like the idea of having at least some explosive grenade option when I'm running Stun Grenades. However, I find the Grenade Pistol kinda wimpy compared to Impact Grenades, and I'll really wish I'd taken the Redeemer if the map has a lot of jetpack bots.
  • Grenade: Stun Grenades. Great for stunning Hulks so I can line up shots on the eye more easily.
  • Stratagem 3: Autocannon. Destroys Hulks (aim for the eye), Devastators (also staggers them heavily), Shredder Tanks (aim for the gap in the turret armor where the guns stick out), Walkers (aim for the hips), Factories (aim for the flap above the weak point, you need to ricochet the round into the factory's guts; requires a front-on angle to the target), Turrets (three or so shots to the weakpoint), 2-taps gunships I think if you hit the engines (4 shots otherwise), even kills Devastator Tanks (shots to the weakpoint; it's also possible to kill one with splash damage to the weak point even when you don't have line of sight, but it's trickier). Edit: can't shoot down a dropship, but AC splash damage in a dropship's belly will kill most small things before they even drop. I make sure to do a half-reload when the gun has 1-5 rounds left so I can avoid the charging handle animation.
  • Stratagem 4: Swing option, depending on how the team loadout looks. Could be an EMS Mortar turret if I think we need more crowd control, or an Eagle 500kg if I think we need more anti-armor, or something else I feel like playing with.
  • Booster: Whatever the team needs, in this order of preference: Sprint > Vitality > Ammo > Muscle.