So, let's take the Fungi/King camp specifically. In my experience everyone wants the following group make-up:
- Cleric
- Tank
- Shaman (Ideally w/ Torpor)
- Enchanter
- Monk (a good Bard can pull but not everyone trusts pickup Bards for this so Monks are preferred)
- Rogue (other DPS will do)
My point being that for every pick-up king group there's a slot waiting to be filled by you. Meanwhile if you're a Wizard or Druid or Necromancer or whatever you
can get a King group, but you have to compete with the more popular options for your slot unless you start the group yourself.
As for most other loot camps, you don't always even need a full group, let alone a perfectly tuned one, but still Enchanters are highly desirable because they are the best CCers. That can make all the difference between a wipe and some good XP when the puller brings too much, so I think it's pretty safe to say that you'll be in demand pretty much wherever you go (although of course
every class has to deal with gluts of their class all showing up in the same zone).