LOL, well you could try fight fire with fire. Try posting some more specifics over on the SR4 specific forum asking for tips on helping your NPCs to have a shot of keeping up with their munchkin antics. Maybe even some tips to curb their power.

Seven players/PCs is going to plug a lot of holes in a team members, but sounds like you've been able to get the team split up which is an excellent start.
Off the top of my head:
A couple of enemies with Counterspelling, one speced to Combat Spells the other to something else is an excellent start. I believe you get an extra die from the team help of the second Counterspeller. The beauty is neither of them need be mages, one or both could be Mystic Adepts with a single Magic point allocated to the Magician side and the rest into Powers. So when all these bad mojo come at them with fists/blades/firearms but you're rolling resists behind the GM screen that sound like thunder they'll be scratching their heads who to geek first.

You'll be adding more than 8 dice to the spell resist rolls of all the enemies. That should really help protect them from that Stunball spell. At least get your poor little NPCs into the second Combat Turn.
Note: You may not want to explain initially how the rules are letting you do this. Let the little min-maxers figure it out themselves. They'll probably even enjoy the puzzle.