I run a this mixed team

DK tank
boomkin
ele shan
frost mage
disc priest

I used to run the standard prot pali 4 sham.

With a mixed group theres pros and cons, heres a few:

Pro:
Buffs
More utility - lots of different CC, dispells for all kinds of debuffs, with duel specing being able to swop from 1 tank 1 healer 3 dps to 2 tansk 2 healers 1 dps if needed and lots more
different armour types means when an epic drops there less chance it goes to waste
solo play - with 5 different classes when u fancy playing solo you have more choice

cons
class weaknesses - e.g. arcane mages suffer from mana usage meaning when 1 char needs to drink you all have to wait
proc based dps - mages / boomkin etc depening on spec gain a lot of dps from rpocs which are very hard to manage as a MBer, though saying that i dont spec for procs or use them if i do and DPs is still good.
class knowledge - dont under estimate this one, having to research 5 different classes can take up a lot of time.


Personaly I wont go back to 4 ele shamn, haing almost the perfect buffs/debuffs in 1 team is just too good to miss.