With the current low player population, I think endgame content like GTH, DMP, and Hell Mode dungeons needs to be nerfed.
The problem isn't only the difficulty — it's the time and number of players required compared to the rewards. When it’s already difficult to find enough people, spending a long time clearing extremely difficult content for rewards that aren't worth the effort makes players simply skip it.
Lowering the difficulty and/or improving the rewards would make this content more realistic with the current population and give players an actual reason to run it.