My decision to roll 4xShammy, 1xPally was completely and totally autonomous. You people, nor those you listed had any influence what-so-ever. In fact, the day the game launched I said, zomg!! I gotta roll 4xShammy, 1xPally!!

Ok... maybe not so much.

Sure the videos play into it, they get the idea in your mind, but if your goal is PvE it really makes a lot of sense.

4x healing totems (zomg)
4x reincarnate
5x rezzing
5x healing
5x shields (significantly sturdier than mages)
Don't have to worry about sheeping - very effective but has to be managed well
4x Heroism (zomg)
No cloth or leather in group (sturdier)
Assundry other totems
Great tanking with Pally + more mana for Shammy
Pretty decent dmg output

Sure I think maybe Pally, Priest, Mage, Warlock, Hunter is my preferred group of all time but they're all so different that it's going to be really tough to get your head around how to handle them all at once.

Rogues are right out
Warriors are out because Pally's AOE tank better, no rage, etc.
Druids are an option, but if you just HAD to heal, you'd have to change form and die (tank wise)
..
..
..

Attention span gone. Any-who, look at it like this. If you're doing a 1x4 setup with your 1 tanking and 4 doing the rest, then the 4 have to be able to heal AND dps. That gives you the following options for the 4

Priest, Druid, Shaman, Pally

Right off the bat Pally is out for the 4 because of melee and that's tough x4. So then you're

Priest, Druid, Shaman

Priest - Squishy... but VE meh... only CC is shackle, blah.... lots of power, all the rez you can want, have to break SF to heal or just not use it... maybe go holy nuke but my impression is that's a little underpowered PvE wise

Druid - Sturdy, No CC, have to change out of Boomkin to heal, only rez once every half hour with reagents... good power, group HoT on timer and channeled

Shaman - Sturdy, Totem CC (which can be fairly effective), good amount of power, all the rez you can want PLUS reincarnate x4. Group HoT for 2 min at a time (limits micromanagement of healing), spell disruption, grounding totems ( <3 ), etc.


So anyway, that's my thoughts on the phenomenon