Further to what the op has pointed out, I would like to add that I find it very peculiar that in order to fight an NPC spawn, usually the rock-paper-scissors foundations does not work.
This game is supposed to be build upon the idea that;
Nuimqol are strong against Pellistal but weak to Thelodica
Pellistal are strong against Thelodica but weak to Nuimqol
Thelodica are strong against Nuimqol but weak to Pellistal
which in short would be normally referred to as BLUE > GREEN > YELLOW.
The way resistances and armor hardeners (against npcs) work is different from assault and below to mechs and above.
Let's take a new player starting in Attalica fighting in his little arbalest as an example. He would follow the above advice and he pops over to hershfield to seek harder green bots that are naturally his arch enemies. He would use kinetic slugs and see that he is dealing good damage while his bot is naturally tuned against these enemies. So far so good. Then he upgrades to his mesmer and tries out some T3 mech-Heavy mech spawns armed with his composite core slugs (pure kinetic) and he soon notices that liquidcore (kinetic+seismic) does more damage, but then he realises that chemo ammo is probably the best damage dealer all round since it provides a little bit more damage and is better vs industrial npc that pops up once in a while.
This story would have been all nice and dandy until one realises that the best robot overall against NPCs is actually the Seth Mk2! Yes an all around robot that overshadows all other races in almost every possible way. Let me explain this a little bit in detail below as per my findings;
Against Green spawns the best is Seth Mk2 with Machinegun chemo bullet and second Gropho Mk2 with sonic missiles. (no Mesmer here!)
Against Yellow Spawns the best is Seth Mk2 with Thermal LCL lazors and second Gropho Mk2 with chemo missiles. (should be Gropho the best no?)
Against Blue Spawns the best is Seth MK2 with Machinegun chemo bullet and second is Mesmer Mk2 with composite slugs (still mesmer tank and accumulator is a bit flimsy)
The above is taken with max skill t4 fits. Now this has been the case even before the tuning rebalance and has been tested these last days. I might be missing some details so in that case please point them out. While I point out that I do not know the coded npc resistance profiles the fits scanned from the npcs and the damage applied to them seem to tally.
My proposed solution:
Fit NPCs with the following: No armor plates - 1 Univ Armor - 2 Univ Armors.
This way the resistance profiles would follow something like this:
No Plates (assaults and below) - This is already the case with lots of assault and light bots.
1 Universal plate - Mechs and above (T2/T3)
2 Universal plates - Elite mechs and above (T4/T5)
And the percentages should look something like this:
Example on Yellow npcs (artemis / seth / zenith)
No resistance plates - 23.08 60 9.09 31.03
1 universal plate..... - 37.5 64.29 28.57 42.86
2 universal plates... - 54.55 70.59 50 57.45
Where the profile follow Chemo - Kinetic - Seismic - Thermal
If this is a good solution, would it be hard/take too much time to implement? To spice thing up, you can also keep the current (or even secret) damage profiles on Rare Npcs (like mighty arbitrer / observers) so that players have to explore and find out new things.
Ps. Something else needs to be done to tackle the fact that most pvp/chemo ammo is straight out the best against everything
PPS. I would like to see the devs create more NPC content as there are potentially more players that are interested in PVE and might find the situation in Perpetuum quite a bit grindy and rigid in terms of going through the mission levels. I am not sure about the tap situation, but it seems they are not much used in their current state.
PPPS. The game is great, just need some more ppl 
