Interesting - Random Dungeon Finder Pool

The dungeon finder tool, takes advantage of the already existing battlegroup (aka closely related server farms). For kicks, I clicked on my battle group on the WowArmory and found a blue post by Nethaera.

The following realms are all a part of the Shadowburn Battlegroup (List subject to change):

Agamaggan- PvP
Azshara- PvP
Baelgun- Normal
Dark Iron- PvP
Detheroc- PvP
Emerald Dream- RP-PvP
Greymane- Normal
Kalecgos- PvP
Lightninghoof- RP-PvP
Maelstrom- RP-PvP
Malfurion- Normal
Moonrunner- Normal
Nazjatar- PvP
Sargeras- PvP
Staghelm- Normal
Twisting Nether- RP-PvP
Ursin- PvP
Wildhammer- PvP

 I find it interesting that most my heroic dungeons are run with PVP players. Of 18 realms, 5 are NOT PVP (including mine Malfurion). This puts a bit of a different light on the 5-man groups that I have joined. Now I am going to pay a bit more attention though.

Have you noticed any consistencies with your groupings? My 5mans are typically:

• Healer = Shaman
• Tank = Pally or DK
• DPS = Me (warlock)
• DPS2 = Mage
• DPS3 = Another Pally or DK.

Is this due to server make 1/5 Normal to PVP ratio, Blizzard maths or simply server population. Are most healers rolling shammys?