My thoughts on the current jungle.
insert unpopular opinion puffin (TL;DR at bottom)
I think the jungle is in a pretty good spot, better than it has been in a long time. Some of the sweeping changes they made to it were just never balanced right and only recently has Riot really put focus into fixing that.
I think the reason most people are so upset about the strength of JGs is they're just not used to it. They're not used to that pressure from JGs that used to happen back in the day. They're not used to a JG being able to pull stats on par with mid/adc/top laners. Lately we're not seeing JG scores as better, but as relatively equivalent to mid and ADCs with the occasional top laner that gets ahead due to a weak opponent. Of course top laners have always been the more consistent force rather than a power spike unless they shut down their opponent. So to me a lot of complaints are from people that expect and feel like the jungler should be weaker than laners rather than on par with them, or they're just not used to that presence on the map as it hasn't been there since what was it Season 3?
Okay now going into Sated Devourer and Elise. I'll cover a few champions that I have experience with.
Playing as Elise- Honestly she's been such trash tier, in this case she just couldn't clear fast enough until they added runeglaive, she couldn't clear her own jungle before a champion like xin took his, and both river minions followed up by enemy junglers feeling very comfortable taking HER jg mobs just to add insult to injury. This all changed with Runeglaive, it wasn't so much the buffs to her as it was the addition of that item that gave her clear speeds to keep up with the others. It makes me wonder if we were missing something all along by not building sheen on her after Hunter's Machete in the past just for that burst on jungle clearing. Now I'm seeing her keep up with mid laners and ADCs well. The key to her is either finding good ganks and keeping a lot of vision up for her lanes, or invading the enemy jungle if she can't. It's all about making sure you outvision the enemy with her to take those positions and get that early lead. If the enemy has vision it can sometimes help do just walk in adn try to Q/W them and continue in your JG to give your mid laner a comfortable position.
Playing against Elise- This is kind of a big deal cause I think most people don't know how to handle her right now. She has that same Q burst potential as nidalee or Volibear when an enemy is on low HP. People sub 40% HP need to be especially cautious. The key to beating her is the same key to her doing well, vision. Keep wards out and make sure she can't engage you in human form. If she can walk in and web you then you're in trouble. Her combo comes from human form->spider form. If you force her to engage outright in spider than go human she loses her mobility, gap closing and burst potential. Keep vision out and don't let her surprise you. As a jungler make sure your JG and mid lane are covered via wards so she can't invade or make a pick on your mid laner. If you can keep good vision on her you can punish her invasions hard and prevent her from being able to gank well more so than other junglers, ALWAYS be wary of her burst potential when you're sub 50% HP.
Playing as Xin Zhao- I think he's benefited most from devourer by quite a long shot. His strength in jungle was always his clear speed with decent sustain, now however his sustain is at all new levels with his still naturally good clear speed. He's a champion that either gets ahead and dominates any fight he picks, or if he doesn't get ahead makes a great follow up champion to an initiate with his ult and knockup which he can now activate faster. Overall he feels very strong. The devourer just meshes perfectly with his kit to make him very dangerous. His knockup especially now that it's 2 hit knockup gives him a gap in the fight to recoup his strength while the enemy is disabled while denying his opponent sustain making him a very dangerous duelist.
Playing against Xin Zhao- Honestly this can be difficult, it's not always as easy as "hard CC him" like yi as if he's not dominating he usually waits for an initiate. I'd say the main thing is watch for his gap closer and instead of trying to outduel him when he uses it back off or knock him back if you can after he does. Find a way to disengage and re-engage on him, or don't let him that close if you can't. A champion he has a lot of trouble dealing with due to this fact is Vayne, even with BotRK smite, a pink trinket, and red buff she can sometimes be difficult for him to deal with, especially if she has a support like thresh or blitz nearby (blitz is another champion that can ruin xins day by pulling him out of position in an engagement).
Playing as Master Yi- It feels like he's one of the champions that has benefited least from Devourer. The effects on him as a champion are undeniable, but his impact on the game and role in it has remained pretty constant. He either does really well early game and shuts the enemy team down with their lacking CC/ability to utilize it or he doesn't. If that happened sated or not he tends to dominate. If it doesn't he continues on throughout the game getting sated and still having that same hard counter of CC. Generally champions he could kill without it he can kill with it, situations he couldn't handle he still can't handle. Super late game when your team is struggling he has the same role and doesn't really do it much better than he did before which is split pushing and backdooring in desperation to find an advantage for his team despite their struggles.
Playing against Master Yi- Honestly not much to say here, it's pretty much the same, wards don't have to be too deep to catch him (unlike lee sin. hecarim etc.) a minimal level of caution and some hard CC on your team will usually go far against him, it doesn't hurt to have a top laner with a bit of mobility and hard CC to counter his split push either.
Other Junglers- Junglers like Lee Sin/Hecarim etc. still have their place as well, they force the enemy team to ward very deep, play passively, or get themselves into a bad position, good ward coverage can sometimes catch enemies out trying to deep ward. They also have the ability to force an engagement the way some of the other junglers can't. They have the ability to really get in deep fast. I don't have as much experience with these type of junglers so I wont go into more details.
TL;DR All in all I think the JG is a much healthier place now and I often see JGs keeping up with other top threats in the game but NOT trumping them or overpowering them. I watched a great challenger game the other day where Elise did really well early, got some strong ganks, but the enemy Viktor did well too and actually shut her down hard, even with her gap closing due to his faster cast animations he was able to burst her before she could burst him. He ended up with a MUCH higher score but her team had better map control and won. It's really good to see junglers impacting the game in a meaningful way again.
As far as what's going on as far as the state of junglers goes and why some games can be so lopsided. I think a lot of it comes from people that stuck it out in the jungle and are bringing back some of their old champs, former JG players that are coming back to the JG (like myself) that still have the mechanics for champions like Elise to perform consistently well with them in engagements, and the every growing hoard of FOTM junglers which seem to outnumber the other two. The "Devourer is OP I'm gonna go play jungler now" group, this is the group that's getting utterly dominated, costing their teams, and generating lopsided results.
As far as Elise goes I think there's also a lack of understanding of how hard she bursts low HP champions from her victims, I get the same thing when I still play AD nid now and then with her Q. I realize my opinion is unpopular but it's somewhat informed although I am not a great player and openly admit that, and of course it's an opinion and people don't always agree which is fine. Either way I'd give it some time before dropping nerfs on Elise, just to give people time and see if they adapt without changing her.