I think 5-man dungeons are fun. They don't need the coordination of raids, and are more structured than scenarios. But for some reason Blizz, more or less, abandoned them in MoP. I remember in wrath, in which I started late, 5-mans were my end-game until I was geared enough, and in a good enough guild, to raid. But now all players have is LFR, which takes everything bad about LFG and magnifies it.
So here are some ideas to fix some issues with 5-mans that people complain about a lot.
1. Queueing, and playing, with random and often irritable or terrible players is not good.
Fixes:1 This isn't really a problem in normal modes, just when 5-mans become difficult (like in cata). So, I propose requiring the achievement for the normal mode in order to run the heroic mode. This way players can be forced through easier content, helping them learn the fights (if they are new to WoW).
2 Make only normal modes available through LFG, this way you can only play with guilds (ideally) or other people on your server
3 In reality this is a problem inherent with MMOs, essentially unavoidable, and only a problem with people who suffer from their selective memory.
2. Long queue times stink.
Fix: Flexible dungeons! normal mode 5-mans can be flexed for 4 to 7or8 players, so when 1 tank and 1 healer queue up, 2-6 dps are put into the group, reducing queue times for dps at least.
3. They can become a grind.
Fix: (Blizz really needs to release 5-mans more often) A better fix is to make them 'mandatory' only for people who need them for gear, like the valor cap is good enough.
4. Heroic difficult has been like a pendulum with a motor.
Fix: Make Heroic and normal modes give the same amount of valor! That way Blizz can make heroics more difficult (challenge modes help too, so heroics don't have to be too hard), but not mandatory.