Long time scourge arrow fan sharing what I think is the strongest poison scourge arrow SC build I've ever played, here's a pastebin.

https://pastebin.com/zSVw1FZ2

PoB details:
- endurance and frenzy charges come from weapon swapping with a +2 min frenz/endu charge shield, instantly swap back to bow and you keep those charges for their duration (not as janky as it sounds as weapon swapping is instant)
- Pathfinder with solid investment into charge generation etc = extremely good flask uptime- Hinder/blind are from clusters
- Wither isn't from the gem, that's only there so I can config it properly, the wither comes from clusters + the glorious vanity jewel, 7 stacks is probably conservative

Offensive details:
- The DPS number we care about is thorn arrows on 5 stacks, I believe PoB shows numbers representing a single thorn arrow hitting your target hence the scaler I applied as in reality hitting an arrow from each pod isn't hard with anomalous scourge arrow
- After a full poison duration of ramping you will reach the DPS shown in PoB, and this seems to translate accurately into the game as I was expecting to do roughly 3-4x the damage of my SST bleed build and that is exactly what it felt like
- The PoB DPS is not including my helmet's focus modifier which has +180% ailment duration during focus, in practice this is a massive dps button on big bosses where you get to properly ramp your poisons-
You can proc your mirage archer clearing scourge set up on bosses whilst attacking with your main non mirage archer scourge, this is some bonus damage for free
- All in all its absolutely incredible DPS when considering its dot damage that is being applied by a skill with offscreen coverage

Defensive details:
- Acro and phase acro- Divine flesh
- IC (can easily weapon swap to get your endurance charges back when you see IC proc)
- Enfeeble
- Wind Dancer
- Aspect of the spider
- Blind- Arctic armor (freeze immune)
- Vaal grace
- Juiced up Taste of Hate + massive instant life flask + other flasks
- Ward (behaves like an extra wind dancer)

Despite being 4k life, it is not a squishy build. You basically won't die in maps, there are too many layers for normal map bosses and mobs to get through, especially considering off screen proliferating clear. Bossing is where you will need some mechanical skill to avoid one shot abilities, but even here you aren't that squishy, I've done uber elder / maven / sirus9 all deathless and UAtziri almost deathless but I'm bad at that fight.

Ward Mechanics
Ward carries the offensive side of this build. With well rolled ward flasks, a 100% increased global defences chest, a nice ward helmet and some nice ward boots you will have 3k+ ward. 25% of that is added as chaos damage, and 25% of that is used for defence too. This does mean that your ward flask uptime is very important for your DPS, but this isn't a problem with enough flask investment.

Investment
It can be done cheap, but my version isn't. I put a fair bit of monies into what I have right now. A budget version would make some changes such as:
- No helm enchant
- No veiled ailment duration helmet mod (this requires prefix locking + veiled chaos and it's not guaranteed)
- No auls uprising which means you lose arctic armor and aspect of the spider
- Probably a drillneck or maloney's nightfall quiver
- No extra curse on the defences chest (you have to hunter orb slam this), replace with whispers of doom annoint which means you lose dirty techniques damage, skin of the loyal/lords is good for budget
- No onslaught or fancy boot mods
- Might be hard to get a good belt with inc flask charges
- Faster ailment damage watchers eye instead of dot multi (or no watcher's eye)
- Cluster's aren't too expensive so that should remain similar

In the end a budget version should be able to still be quite survivable for all content, only lacking spider slows and arctic armor freeze immune. Damage wise I think you should be able to reach 4-5 mill without breaking the bank, which is great for dot dps. Ward gear is very easy to roll with dense fossils so hitting the ward targets is not hard.

Overall I rate the build very highly, I'd say its only weak point is the conditional nature of many of the defences and hence I doubt the build would work well in HC, however for 95% of your time in SC you will actually feel rather tanky, I say this after playing SST bleed glad with capped block and life on block. If your a long time scourge lover you need to try this version of the build, having more fun with it than I did with alberons strength stacking.

Edit, dont have time to put together a proper showcase but here are some quick videos. Shaper was the only frag set I had and I didn't play particularly optimally in terms of spore pod placement but as you can see it doesn't matter much.
Video of random map clear: https://youtu.be/oyu3sb0z91o
Video of shaper: https://youtu.be/8naGI3hrXdk