Starting off with the duo lanes.
You are losing roughly 1 XP per non-cannon minion and 4 per cannon minion. This means that roughly every 12 waves (6 minutes) you have lost 1 caster minion of XP each. This means that at 7 minutes - a time at which point the junglers are at or about level 6... almost nothing has changed.
Level-up threshholds, wave by wave, presuming that you aren't missing any or getting any XP from any sources, don't actually change for the most part. There are a couple of threshholds here and there where a specific level up is delayed (but doesn't mean that the next one is) but that means you've never missed a minion and have no extra XP from kills, assists, ward kills, objectives or jungle camps.
In terms of solo lanes, you are gaining less than 1 XP per minion. This means that to gain 1 caster minion of XP extra it takes some 30+ minions, or 6 waves. Every 3 minutes you have an extra caster minion of XP.
What you can surmise from this, is that solo laners get 3 caster minions of XP in advantage over duo laners per 6 minutes. It takes a further 12 minutes to get your 3 melees for it to amount to a whole wave of XP and 6 more minutes **if you want a cannon wave worth of XP in advantage for a total of 24 minutes of uninterrupted XP before you get 1 wave worth of extra XP advantage as a top or mid laner. **
With the numbers put into a more quanitifyable manner what I want to know is... what impact do you think this _actually_ had on the game? Sure, a minion of XP here or there can make a huge difference in lane since it gives people windows of opportunity. In a macro sense I don't think these changes had any impact at all though.
Let's talk about the jungle.
Total potential XP available is up, practical XP is down. If you kill camps perfectly on spawn it's theoretically possible to be XP positive. It's damn difficult. Camps are closer in value overall, with Gromp and Krugs being worth noticbly more than Wolves and Raptors.
Standard level 6 timing for a farm jungler has moved from 6:45 to... 6:45. You still get level 6 off of your third buff if you powerfarm. In any situation where you get delayed, level 6 timings are still really similar to before.
Where things HAVE changed is that when you get behind you can actually get _behind_. I cannot pick Camille or J4, do red, gank, do blue, gank, do crab, back, gank and then do 1 clear and be the same level as the enemy jungler as you could do before. Isn't this a healthy change overall? Yes, it's a nerf to perma-gank junglers. Most of these junglers are also single-target junglers who are buffed by getting way more from their gromp kills. The winrates of Camille, J4 and Xin Zhao all appear to be up in the jungle signifying that whilst the changes make their play patterns healthier (they actually go kill camps) they're also not gutted by the changes.
Objective control junglers are also absolutely huge right now. Warwick is rocking an absurd 55% winrate, AD Shyvana's winrate is around 55% (with AP builds performing poorly). Top junglers by winrate include a diverse range of playstyles, including Warwick (tank/objective control), Volibear (tank/aggro), Shaco (assassin/aggro), Mundo (tank/farm), Udyr (bruiser/farm), Elise (assassin/aggro).
The only junglers that seem to be doing poorly are the "level 6 and go" junglers. I'd guess that this is because a lot of them don't have that great of clear speeds, meaning that they aren't necessarily able to keep up with powerfarm with the increased spawn rate. The only exception to this is Nocturne. That said, some "6 and go" junglers - like Evelynn - do have good clear speeds and so it is hard to say exactly why they are hurting so badly. Possibly because a lot of them don't have strong early games (they're ult reliant) and if they are set behind it takes them longer to get back into the game than it did previously.