Magicians summon spells are actually spells inherited from druids. Druids get these same ward summoned spells a couple circles earlier than magicians and at the same level range that clerics get their ward undead spells. Enchanters specialize in illusion and charm spells. Druids are never able to touch the former but the latter is acquired for taming animals. This allows druids to tame those mighty griffons and use them to do your dirty work for you.
Necromancers have two main areas of expertise.
Druids have no mastery over undead however they do have a mastery over summoned beasts. There are many less summoned monsters in the world however druids can quickly dispose of those that exist. Druids have powerful DoT spells in the form of the stinging swarm line of spells. These will eat away at monsters over a period of time. On the equipment side of things druids are somewhere between a mage-type class and a priest class.