These are my recommendations based on a few days of the Endless Wave event - my current score is 2394 comprising Scorcher 822, Firebug 554, Blazia 695 and Ignus 323
Here’s some footage from the 695 run - I didn’t notice the enemy that got me until it was too late 
Loadout recommendation:
- Weapon:
- I prefer the Plasma cannon - the enemies spawn in a clump, so the plasma blast usually damages many enemies.
- The Looper’s piercing gives a headstart on Ghost, and is handy when we only have 8 perks so would be good too (the Laser also has piercing but I wouldn’t recommend it because it needs more room for homing to work)
- I haven’t tried the Gemini Laser, but it may work well, especially on the more open layouts.
- I wouldn’t recommend the Laser even though it has piercing because it needs more room for homing to work
- Armour
- For most people Ninja will be best because it has a +20% dodge bonus on this event, and it’s what I used for my runs so far. But at higher levels on a good perk build I think the Necro would work better
- Gear
- All the enemies are Flying, so best loadout would be Flying + Flying (if you have 2 well developed Scope/Plaster gear) or Flying + Ranged (with a good perk build the ranged enemies are more problematic than melee)
- It might be useful to use the Shield Generator as the Ranged Gear - if it procs then you will have the safety bubble throughout the run; if it doesn’t you still have the ranged damage
Perk Recommendations
The ideal combo for Plasma (and Looper) will comprise of
- Piercing + Ghost
- Homing + Super Homing
- 2 Spreads + Multi
- Ideal 8th perk would be one of (or two of if using the Looper) Triple Multi, Vertical Shots, or Chain Shots (more useful with the Looper than Plasma)
- Less ideal but still good - Sustained Fire, Death Zap, Double Barrel, (or Ice + Improved Ice if using the Looper)
Notes on perks:
- Bouncy walls can be an option instead of Ghost (and probably will be the way to go if using the Gemini Laser).
- The spreads + super homing pack a better punch than double/triple/quadruple barrel (because they weaken your shots), but they are still useful even if you don’t have homing
- LifeSteal (maybe with Great Lifesteal) is useful to regenerate health, but at higher levels it doesn’t heal you fast enough to compensate for the reduced dps of not having the ideal build
- I don’t recommend dimensional because it only passes through once and they don’t super-home after that:
Other tips
- Most room layouts have a place you can hide behind and use ghost - above the boxes in the video above is not ideal because a missile hit on the boxes can get you; also you can’t evade by going down.
- The ideal rooms are where you can stay at the upper left / right with a big barrier in front (can also block the missiles) and you are on a small platform that allows movement in any direction
- If you have the ideal build, the shot to watch for is the homing piercing double shots (the one that got me in the above run). The laser can also get you but you have more advance warning of that