A big problem with the shortage of tanks/healers is how wonky the queue system is. I've had many FC members and other acquaintances ask for a tank/heal to JIP, but then when I try to jump in and help them out, I'll get shunted into a brand new run instead. I honestly think in-progress runs should take precedence over new runs even if the new runs are technically before them in the queue. The in-progress run has one or more people that already have time invested into it, plus it has a hard time limit on it.