As I setup the pa, I tried as some one suggested
"Use a pair of XLR-TRS adapters and go into line inputs rather than mic inputs"
This did not lower the level coming into the mixer at all.
The line input should be 20dB lower than the mic input, assuming it's the WZ3 series. The pad should offer another 20dB of attenuation. HOWEVER, if you have the original 16:2 it looks like the TRS is just parallel with the XLR and there's a 30dB pad that affects both. That would explain why there's no difference in level. In this case the additional pad seems to be the best/simplest solution.
Exact model numbers at the start would have been helpful (e.g. WZ16:2 rather than "Mixwiz 16" to distinguish it from the WZ3 16:2).