The problem is not only the missing mid-tier challenge, but a big problem lies within the tomestone gear. It is so good that it makes every other content except savage raids obsolete. Why investing time to get the normal mode raid gear, relic gear or 24-man raid gear?
Just run expert roulette and you are good.
The whole (gear) progression in this game centers around savage raiding. Normal mode gear is obsolete on release because of crafted gear. And then you go into the savage raid and when you don't get loot you can buy the tomestone gear as a safety net.
In the odd numbered patches people can "catch up" with the gear. But catching up for what?
This whole concept doesn't keep in mind that there are lots of people who have no interest to enter savage raids. Ever.
And the content these people are interested in does nothing for your character progression. You can't get better by playing this content, you just are getting new glamour gear while you are actually using the freebies from expert roulette.
The progression leads to savage raids and nothing else. No wonder all kinds of people end there even if they don't have interest in doing that content. There simply is nothing else meaningfull to do.