I'm running an almost all Wizard campaign. I have five submerged level wizards and one biomancer focused practitioner. They have not lacked for a challenge so far. They thought that the Red Court Vamps were push overs until one actually got to grips with one of them. Then it quickly turned into panic, fear and a badly hurt wizard. It wasn't my intention to make it into a lesson or example; but that is just how it turned out.
I have also found that most wizards REALLY lean on that Lore roll substitution for Alertness against supernatural wonkiness coming at them. Especially in my group where I have 3 wizards with a Lore of 5. So, the biomancer saved their bacon when she was the one that noticed the mortal goons waiting in ambush with automatic weapons. Which, for me, brings up a good area for other character types to shine: Skills. Wizards, mostly, will have to stack up their Conviction, Discipline and Lore as their top tier skills. And, yes, they have Thaum to fall back on; but that takes time. Even for my Lore 5 submerged wizards that can drop a complexity 5 to 7 spell without prep. Simply craft your story such that time is not a luxury item. Then that character with, say, Burglary really comes in handy. He can be through a locked door (subtlety that is) before the wizards finish talking about HOW to craft the right spell to do it.
The social skills are also a good, easy place for other characters to shine. Again, wizards have generally stacked up their 3 base skills. Not things like Deceit, Empathy, Presence, Rapport and Intimidation. Those can be huge elements of any given story and are not easily substituted by magic. At least not without skirting a Law or out-right breaking one.