All that makes me think that I haven't been too good with the wizards. I didn't let you much time to study new spell, transcribe scroll or make magic items.
When I builded that story, there were no wizards in the party only a sorceror.
I also must admit that the sewer part wasn't made to be tackled with the brute force approach. But Jasper seems to just saved the day so I don't worry too much, we will see what happens next.