Back during the heroic end time dungeons I ran:

Prot warrior + rshm + 3x MM hunters.

I found that to be ideal for running dungeons. I guess disc makes more sense than the rshm because of the number of instants.

There are a number of reasons why melee are harder. The main reason is the way AE works. AE fired like a volley across the room at ranged is easy to see and deal with. The same is not true in melee range. It tends to land just before you react to it, every time.

Melee are also tough because of IWT. If you press it just at the right time you'll get a runaway. Like that window between touching the mob and the next keypress wasn't significant it will just keep on going as though IWT never happened.

There is also the problem with view clutter. A tank standing in a hot zone alone with the boss is an easy eye thing to spot. Throw three melee in there with him spamming effects and it becomes much harder to always spot the hot zone coming.

I don't view melee as easy whatsoever and I would not recommend that someone play a full melee squad in dungeons. That said, if you want a team that can do both PvP and PvE, a full ( or at least mostly ) melee team makes sense.

I may be doing this soon on my rshm + 2x enh + 2x war soon. Things that I already do that may be helpful:

Create a combat assist macro that works through WoW's /stopmacro functionality to set an order for targeting mobs. It goes in priority like: FTL assist found target? > Tank found target? > Target Enemy. That keeps them from running all over the place selecting their own targets.

And of course as stated in another thread, better to move the tank than the DPS if an all melee squad.

For stuff where you need to move everything at once set a toggle to switch between the primary and group. Like in Timeless Isle on the ghost ship fight I had a toggle for my entire team to move at once together. I found it super useful for that fight and the elites that ground slam too fast to respond to ( those fights I just spammed the move key while fighting them ).