It's been a long time since I've played...

You used to need:
- a tank
- a healer
- a haste/slow guy (Enchanter or Shaman, not usually both)
- three more with damage dealing ability

Tanks used to be:
- Warrior (hardest to hold threat, lower damage, far superior mitigation and hence healer mana efficiency)
- Shadow Knight (very easy to hold threat, dps could go nuts almost immediately, not as good mitigation)
- Paladin (similar to the SK as far as threat/tanking efficiency, but more secondary heals and less dps)

Another consideration is a puller:
- A feign death class was an asset.
- Especially if it wasn't your tank, so you could chain-pull camps.
- By the Planes of Power era, a Bard with brains had the tools to outpull anything.

Not sure that you still need a Necromancer, but they used to be the only option to get your corpse back in many zones.
A rogue was good in many places for that too, but see-invis/stealth mobs sucked in places.

A friend said bards basically twist their own songs now.
Rather than needing to push "1" (start song A), "1" (end song A), "2"... etc...
To "weave" 3-4 songs at once.

Necromancer had Dead Man Floating, for water breathing.
Druid had Spirit of Wolf, which was huge.