Kind of hard to be sure what you are after here. First you say you want to do scosglen farm and all ubers, then you finish with just easy dunc/fauzt on set. Those require very different things.
For easy dunc/fauzt on set you should already be able to do that with summoner necro on the set.
I used these guides in the International Forum to get started on my SSF journey this season:
viewtopic.php?f=28&t=69236&start=50 . It's in a language I don't understand, but at least in Chrome you can just right-click the page and "Translate" and it's in good enough english for me to understand.
I've just done the summoner variant with Satanic Mantra set, Graven Image shield, Truce belt, and Kali gloves (I should really make Aiwass). Priestess (Act 1) merc with full Bow set. And Iron Golem from a T4 Naginata TU (Na-Krul's Spine). With that I can just teleport around Fauzt and stuff dies. Same in Dunc obviously, but I like Fauzt better cause my Merc just strolls into barrels in Dunc.
It's a great starter for SSF for sure. I've found literally every normal set so far (the ones that can drop in K3K), and it's helping me fuel my alt addiction. I think I have every class except Sorc well into Hell now, and I can't decide what I want to push hard on (like you), but that's fine. I love trying new builds more than pushing one to the max myself. I just kind of go where ever the drops I get take me.
I kind of want to try the XBow setup on that same International guide, but I've yet to find any of the Zakarum set sadly. I also want a character that can farm me all the charms my Necro can't. I have a Clawsin at 125 that seem to be able to just facetank most so far (with set), but is to boring to level higher. And a Stormzon that just crushes some bosses with set, but is a bit to squishy for my liking.
For scosglen, all ubers and labs you kind of need to either trade or farm A LOT no matter what build you choose I think. Although, I'm actually farming Scosglen ok with the summoner necro with the same setup mentioned above. Can even kill the druids with enough effort. But it's very slow, especially the trees (I don't think I understand how they work though). And it requires lots of resummoning. The Void Archon aura and 20'ish summons make it doable cause you don't get hit very often, and you're far from getting one shot. It's not very fun though imo, so I tend to just stick to Fauzt/Brem when I play the summoner.
Anyways, there's tons of builds that can do Fauzt/Dunc farming well on fairly easy to get gear - and there's quite a few builds that can do Scosglen/Labs well with good gear. And I'm guessing tons of builds that can do it all with perfect gear. So if you really wanna push the late late game content, I suggest picking something you enjoy playing and just keep pushing it to the limit. I haven't found that poison yet myself, so I'm probably making another alt.
