I say at level 11 for a wizard a summon monster 6 is a god send If a party doesn't have a healer summon unicorn thank you!
Summoners shouldn't just use summon monsters in combat a dog can track and squid can swim you broaden your skill selection by alot believe me we have a sorcerer summoner in our party and she does fine, she is a delayer against the foes until we can get our bearings.
I'm playing a wizard even though I'm great when a fight breaks out she fills the role of tracker/healer/ scout/delayer/nature survivalist.

I only take up buffer/damage dealer and partial skill monkey.

Okay she does all those thing quite well and I'm very specialised but thats the cost and i like having her in the party.