I know you can complete all zones at level 100s, as they are freely choosable. I did not see any level requirement on artifact talents or skills on the beta and I know one person can get much further by grinding artifact power than someone else. I don't know why you keep talking about relics, but if you complete the zone at level 100 you get a level 100 Artifact at the end. Both rare and uncommon relic drops are also usable at level 100 and grindable. Quests inside your order hall work at level 100 and grant you the uncommon and rare relics as well.
One thing that could ofcourse be the case is that you can't gain Artifact Power if you freeze your XP.
Apart from that I don't know what you mean. I mean I get what you're saying that Blizzard probably wouldn't do that for the sake of level 100s (and they probably did not do it for that), but I also thought it's anti-Blizzard to make PvP completely unbalanced again against the lower-level players in a bracket, especially after how well the scaling was received, yet here we are.