2. Well... They can nuke, but sorcs nuke better. They can heal, but clerics heal better. They can fight... Fighters, Rangers, Barbarians, Monks, Rogues fight better. They're able to do all three... but not exceptionally well and after a while the versatility comes at a steep cost.
3. Nothing like DnD. As a lovely example...in PnP Druids get some Mass Cure spells. They don't here.