You arent even discussing end game balance, you are discussing game balance. You have evidently decided that the only input considered should be build meta theory crafters. People like you dont want to raise their own difficulty, they want to control EVERYONE ELSES. One of the biggest reasons people wanted to see this game come back was that it was so easy to set up the experience you wanted to play. Then the other shoe drops...People have this itch to control other peoples rewards. "they shouldnt get rewards cause they arent playing how I want them to play" we arent competing, other peoples rewards have absolutely nothing to do with you. really, they dont.
leave the game balanced at lvl 50 with so's. do a little balancing between sets, buff up the under performing, trim down any extreme outliers. You will never really get true balance between ATs without either homogeonizing them or completely re writing the game. If you want the game harder, take control of your own experience and make that harder. You do you. The devs have very limited resources and they will be unable to rewrite endgame to suit you. When approaching things like TW, try to balance trimming damage with a little improvement of mechanics if possible, some good with the bad.
Just as a point of reference, WOW just implemented a new leveling set up, with leveling a new toon to cap in 7 to 20 hours. thats playing dungeons and missions BTW.