They should just make it Boss > Boss > boss > Boss > Boss, if they still decide to go the route of not making the mobs actually do anything. Wooow, the mobs are doing a super telegraphed AoE around itself that I can stand on and maybe lose like, at most, 50% of my HP? That's craaaazy.

How about add in tank busters (cleaves the front, so ppl have to look where they are standing), add raidwide damage, add random mechanics where a mob maybe suddenly starts chasing a random player so the healer has something to heal. Add fun buffs, like if you kill a pack of mobs before their buff runs out, you get that buff for yourself .. and it could be the speed buff from CC/PT, or a damage buff, or a haste buff. Add casts that if they're not interjected/stunned/slept, will give the mobs all a damage up or vulnerability down. Add random environmental effects, that if you drag the mobs over to, they will take a vulnerability up. Add an esuna, but you can use it on enemy targets, and make mobs get powerful buffs that you can then remove.

Maybe remove walls and make just a big open spaces with mobs and a boss, and you have to kill a certain amount of the mobs before it lets you get out of that area, with varying mobs with different mechanics that the party can decide on which to do. Is your DPS high? Go for the mobs that have more HP and will count as 2 packs defeated out of 6 to progress, but if you fail the DPS check, they will explode for lethal raidwide damage.

Design mob packs to allow for creative uses of your tools. Stuns, interjects, invulns, repose, rescues, your mobility buttons, personal mitigation and heals like second wind + bloodbath shouldn't only be useful when a healer dies, or if you got aggro for a second.

And for anyone that this is too difficult for, make a trust version where you can RP walk your way to the end, maybe have all the people you've met along the way line up on both sides, clapping and congratulating you while 'Close in the Distance' plays. Maybe call it 'Endwalking' mode, because you are walking to the end of the dungeon.