At level 70, I had a powerful character with decent gear and all the right aspects. Every level, I get one level weaker compared to the constantly “upgrading” enemies. For example, the Butcher who I toasted at level 70 two-shot me at 83 because I am in the same gear and he has +13 levels of stats.
Please allow us to toggle off exp so we can keep our relative power levels.
Actually toggling experience off would allow for more content and depth to the game. I love Twinking characters at different levels in WoW. Also there is a big LLD (low level dueling) community from D2.
This would only be a good addition to the game to add more things to do and work on.
You should spent your 52 paragon points. At level 70 item give horizontal upgrade. The vertical upgrade come from Paragon board.
Interesting idea, it could allow for groups of friends to stay at a similar level if one wants to play more often. They can lock their character and still farm for gear.
They would need a fairly large icon on the screen that reads NO XP or some such that is easily turned off by clicking. Then you make it take 4 or 5 clicks to turn on.
Never underestimate the customers ability to mess things up. Somebody somewhere will complain “I’m not getting XP and I demand a refund for this broke product or I’m calling the BBB”
But do you mean you are wearing gear from level 70 at 83?
Or 70 level gear fighting a 83 butcher?
Okay i think i get you.
I am going to suggest you look at the gear, check thr stats and see in the upraged gear preview window,
Make sure that you can’t actually go higher or add more stat power.
If not, idk what is wrong.
People say gear doesnt matter i disagree the numbers go up, and you need to sometimes take that power and imprint it on a new yellow or find a better leg.
Has been the game for me, doing this the scaling means not that much, i OP everything white level and early orange, late Orange and RED and the challenge curve goes up like it should.
Actually you can go in town there is no xp there, unless you return a quest. Also you can collect item at the merchant and ask gold from other players. This is a solution for you. 
I hope it help you have fun.
In WoW you spend 10 gold to turn off your experience at an NPC. Then spend 10 gold to turn it back on. Twinking is a huge part of the game and adds so much content which is why people spend countless hours on it.
In D2 people stop at various level and spend months or years collecting expensive gear for them. Don’t matter if it’s 19 or 30 level. It add a lot of play time and activities to a game that is lacking depth and things to do.