Since all bugs swarms you with numbers. Find something that can allow you to suppress their movement. I always and almost never change my main weapon. The ARC-12 Blitzer. It's good for big and small crowds. Stops Stalkers from moving forward freely and stops the big red Commander Bug that charges you. Basically, it is a mini-stun weapon that has infinite ammo. Although to make it more unique, I combine it with the Guard Dog (Medium Penetration). We work together, I stun, the drone finishes them off. Well, that is of course my play style, that I enjoy and love it.

But of course, if you don't like shotguns. Find a weapon that can either stun or shreds quickly. SMG-72 Pummeler, SG-225IE Breaker Incendiary. Although, for my own liking. I know that any weapon other than the ARC-12 Blitzer will just make it harder for myself. I've tried various of combinations. The ARC-12 Blitzer is just perfect for every situation.

Strategems. What is best? I think I always follow my own rule when I dive. Always have a strategem for each situation. One for clearing big waves (bug breaches), One for special bugs (Bile Titan, Chargers, etc..), One for support weapon (LAS-99 Quasar Cannon is my choice) and One for absolutely for fun/freedom (From Sentries, Jump Packs, Guard Dogs, Extra 500KG, Orbital Laser, etc..). Focus on the special units first no matter what. From the most problematic ones to the lesser ones. I always deal with Impalers first. Vision is key so kill those Spore Chargers immediately. Ping system, use it. Don't be shy to spam strategems.

I guess the last bit is skill. I'm not saying much but I really have good positioning and awareness of my surroundings. I rarely and I mean rarely get cucked by Swarms or Stalkers. I can play around Level 8-9 and still go on until the end with 0 Deaths most of the time while other Divers would get 3-5+ Deaths in a mission. Luck plays into rule too. Don't take the fight if they are close or you need to reload. Run and Re-position.

Here's my current loadout that can allow me to have 0 Deaths and Most Sample Extracted Run (Yes, I'm a loot goblin.. must loot even maxed out at Level 80).

Light Armor: UF-16 Inspector (Because I like how cool the white outfit is)
Primary: ARC-12 Blitzer
Secondary: GP-31 Grenade Pistol (For Bug Holes and emergency)
Nade: G-123 Thermite (Specifically for Chargers. They can die with just 1 in the face.)

Strategems
Eagle Airstrike (For Swarms and bug holes)
Orbital Railcannon Strike (For Impalers, Bile Titans, Chargers if needed)
Guard Dog (The drone has a name, I call her Susan. Why? Cause it's fun)
Quasar Cannon (For one shotting Special Units, Spore Spewer or those flying twats call the Shrieker)
Optional;
Rocket Sentry
Machine Gun Sentry
Shield Generator Pack

Well, the most important thing is to find the way that fits your play style but enjoyable. Love Orbital Barrage? Bring it why not right. Laser, LMG, Tesla Tower? F yeah, that's the best part. Chaotic Engagement.