While I'm expecting to get downvoted for saying this, "ELO Hell" is generally the rank a player truly deserves (or slightly below it).
When your level of skill is significantly better than your current MMR, you can carry games rather reliably. When you MMR is significantly above your current ranking, then you will earn more for each victory than you lose for each defeat and you can quickly climb even with a 50% win rate.
ELO Hell is the point where your MMR is approximately equal to your current ranking and you are no longer more skilled than the people you are being matched with. That is, when your MMR and ranking have reached the appropriate placement for your skill level.
You have to deal with feeders, leavers and trolls at all ranks of the game. You are not immune to them in Gold. You are not immune to the in Diamond.
The thing is, players are equally likely to be subject to those players. Over a large enough sample of games, it will even out; you will have won a similar amount of games due to leavers/feeds/afks as you have lost due to them.
While I've not looked over your profile (so I'm taking you at your word about your play-style and skill-level), I would recommend you try to adapt your playstyle (and picks) to the ELO you are playing in.
You said that you focus on roaming and helping your team as a jungler, which is a prefectly fine play-style when you are with Platinum and Diamond players. However, it tends to focus on coordination with your team and relying on their competency to not throw away the lead you have given them.
It may be a good idea to try a more selfish play-style; focus on getting yourself fed enough that you can hard-carry the game even without the help of you allies (i.e. meat-shields, distractions). Focus on out-farming the enemy laners and getting strong enough to solo-kill them even without assistance, then use that advantage to take down objective after objective
If you want a couple examples to watch, I would recommend Trick2G, Nightblue3 and Sirhcez. While they aren't professional players, they are quite skilled and their play-style tends to be rather selfish. While they do assist their teams heavily (since they are in Diamond), their playstyle is generally centered around controlling what the enemy can do and getting themselves strong enough to influence the game with little help.