Join in progress should probably join a party in progress?

[ElHeggunte]

It actually really bugs me that there isn't a way to invite someone into or select a specific in-progress instance to join.[...]

Join party in progress should bring up a list of instances looking for members and list the player names and respective classes, that way you see [...]

More transparency would just invite abuse. They won't do this for the same reason they removed the "In progress" notifier on the queue window and added a penalty for repeated withdraws: it keeps people from cherrypicking runs, leaving some groups stranded indefinitely. The current system also attempts to ensure that older groups get filled first. If we used your suggestions the entire system would immediately devolve into a clusterfuck with most stranded groups getting stuck in an infinite queue limbo. It'll also have a severe impact on the number of fresh groups being made, slowing down the system for everyone.

People may attempt to use it as such, but Join In Progress was never supposed to be something you used for your own convenience.