I know this is an old post, but quick correction on Dispel Magic. It allows you to end a spell on a creature or object, or end a magical effect. Creature and Object are obvious, but magical effect is a state that is induced by a spell, not the spell itself. You end the earthquake caused by the spell, you do not end the spell earthquake while it's being casted. You also need to cast it as an action, meaning that it cannot dispel an instant effect spell like Fireball. Still really great, but not for the reason you outlined.
For things like Fireball, you'd need Counterspell. Having both in a party is great, Counterspell for attack spells against the party, Dispel Magic for those pesky progress blockers or status effect spells. Note that it let's you select an effect in range, not one you can see, so if you know an enemy just went invisible, and the enemy hasn't left the range, Dispel Magic will handle it.