Everyone's ranting about the bard today. I may have something to say about them tomorrow, but I just want to do a short post today.
Remember potion miscibility? Here's a crazy idea: what if, when two magic-users fire wands at each other in the same round, you treat it like mixing potions? No 1 in 6 roll to see if it happens; it's a rare enough situation as-is. Just make a reaction roll, and if one wand is supposed to have a reduced or cancelled effect, it's the wand used by the M-U with the lowest Dex.