Summoners don't seem too bad in the damage department. They are fairly on par with dual wielding creatures through the first few levels, but then tend to sort of fall behind their companions once multiattack and fireball are achieved.

One thing that summoners could use is cantrips. They seem like a class that should get them, as they don't have any class features that encourage them to use weapons, such as the other half-casters, the ranger and paladin.