Good job OP and supportive forum members, we got 1/2 way there!
"Backstabbing characters no longer provides Advantage on attack."
Now they need to address height advantage and not needing any stealth check to hide with 100% reliability outside of cones of vision.
Fixing that part of stealth would be nice, but I believe the bigger issue by far is Hide being a bonus action for everyone. Make it a full action (except for the Rogue of course) and Hide for advantage is already much less of an imbalance simply due to action economy.