Don't mean for this to come off the wrong way, but after failing an encounter for more than an hour, i'd be inclined to realize that something is being done wrong. 4 hours is insane.
There's only so much trial and error you can go through before you discover that there's an inherent problem with the approach. My Skolas attempt on Arc burn was unsuccessful for around 45 minutes until I started using a rare Arc sniper. It wasn't anything close to 365, but that alone gave us the extra stun and DPS we needed to defeat him.
On Void burn, i hardly used stealth for Hunter. Once the bonds were broken and Skolas was weak enough, we'd run to the mines as a team. This is of course dependent on Skolas not putting his feet up on the one mine, but I can't imagine that he'd be there enough for the run to be unsuccessful for that long.
What was the main issue with the run? Stealth is certainly helpful for the mine part, but on Void burn I don't think it's a necessity.
First, just to make sure I'm not confused about some mechanical aspect- both the servitor bonds breaking and the mine waves spawning are based on hard HP thresholds for Skolas. i.e., you can't have the mines spawn without the bonds having been broken first.
I'd love to admit to you that something was being done wrong. I'd love to be able to say that in hindsight I simply held our group back by failing to do something or giving incorrect instructions. But I can do nothing other than generically disagree. Watching Mindlog's video in particular it is clear we were approaching the encounter in the same way. On our best attempts we came close to simply succeeding, in the same way, but did not. Even in the context of that success, there are a couple of lucky "rolls" as far as which mine spawns where and which guardian is tainted at which moment. I would love to hear that there was some inherent problem with the approach, because I would have been rather reassured if it seemed that we were doing something wrong. I'd prefer the notion that we could have just changed tactics and succeeded- rather than acknowledging we were doing everything right, but not well enough. It just seems like the latter was the case.
There was no "main issue" I could identify. We made "regular" progress (we were getting him closer to dead more frequently during the last few attempts than the first). All signs pointed basically to our group being
able to beat him, with continued persistence, adaptation and a little luck on the RNG aspects, but simply ran out of time to be able to continue trying.
The biggest pain point for me was that sometimes he'd "slip by" during our first DPS phase and teleport, sometimes even twice in a row, and thus be way too close and hard to hit to do the damage necessary to even break the bonds before needing the second servitor. If we were able to do that every single time the progress would have felt more natural, but for ever 3 or so runs where the necessary DPS was done to break the bonds, there was one where he started teleport-hopping and we had to hunt for the second servitor. I still have no concept of where the inconsistency with this part was coming from. But it would be totally unfair to call that the "main issue" because we did get past that phase, sometimes very easily, a number of times, and still couldn't quite make it through the rest of the fight.
It was a group formed of three people who had never completed it before, and fatigue was an issue at least for me. I didn't hit every single headshot. Sometimes I missed captains on my radar. Got wire rifled a lot.
You're free to consider 4 hours insane... for my first Atheon kill it was 6, HM Atheon was somewhere around 4 or 5. HM Crota was over 10. All of the above over two or more nights. I honestly don't have the slightest issue with those numbers. It ought to be hard, and require patience and perseverance. It ought to be a significant barrier to overcome. My main frustration right now is that I simply can't go back and try again, even if my fireteam was willing. It's a rather different fight as of reset, with all of the key HP thresholds shifting in importance due to the extra persistent DPS afforded by Black Hammer and Gjallarhorn, and of course with the extra danger that comes with his Scorch cannon being solar. I don't mind taking my stab at this challenge, but it isn't the same one I've been trying to conquer, and so I just have to put all that empty progress on hold, and that feels pretty bad.
edit: Started at 11 and called it quits at 3:00AM, so it wasn't actually 4 hours on Skolas burn on the PoE 35 in total