I was ok with the old diadem, and the new one. Still could obviously be refined a bit, but a lot of the criticism on forums is a bit over the top. At least some of the enemies there have a chance to KO you, and they have enough HP that you can do proper rotations, and it's not as linear as standard straight-line dungeons, so it can't be all bad. It's a nice side content with nice rewards. Sometimes you get lucky and find a legendary clan mark log, or a rare minion, or a gear piece with good stats. For gathering it's also now the best way to collect certain materials or earn scrips fast.