4 man dungeons are no longer challenging because the gear curve has far outstripped their release. Try the latest (Qarn/Sastasha/Snowcloak) without Poetics or Soldiery and see how they feel, at least numerically speaking they are more challenging even if the mechanics are not.

I'm not justifying SE's continued release of content that is basically outgeared and irrelevant at release, but the way they've decided to tier content along with the existence of tome gear basically makes it impossible for them to create a relevant placeholder for dungeon rewards (Niches filled by tomes/24 man raid/Coil) - and as a result they're basically vehicles for tomes instead of something meant to be challenged.