Delves are pretty much perfect imo but the one thing I would wish for would be the ability to accept a queue and retain your progress on the delve you were running.
I commonly run delves while I’m waiting on lfr or blitz queues and the queue finally popping is great but it’s more often than not when I’m 75% through the delve… Leaving the issue of - do I cancel the queue and finish or plan to rerun the delve?
It would be really neat if there was some kind of “save” option, dependant on reaching the save point or achieving the first objective so you can jump right back in where you started.