There's also the Spirit Wolf (learnable from Viviane) which is great when dealing with enemies that can only deal Penetrating/Crushing damage and it can inflict Bleed for damage-over-time.
But yeah, once we get access to Level 7 there's another summon we'll be able to play with that's likely to be quite powerful given that it's earned from a quest (Ring of Fate) and doubly-missable since it's not an automatic reward for completing it but requires you to do something optional during the quest, then do some specific actions afterwards.