We have raids for 10 people, fractals for 5…
Make dungeons solo/duo content…
Increase rewards based on the (reverse)number of players that entered the dungeon (not the ones that finished, to avoid grief kicking) and maybe the time it takes, give it a just few tweaks, as most of them are already soloable and let people have their fun.
If you can solo it fast you get max rewards… You can still 5man it getting average rewards (or the bad ones as it is) but the faster you finish it the better the rewards are.
Set a cap for maximum and minimum rewards…
I think this would bring back some fun to dungeons. Make some nice rewarding instanced solo content while still leaving it open for people to complete them easily with a group of 5.