>But deafen has some pretty nasty downsides and there aren't a
>ton of "deafen preps" in the game.

In a raid deafen has disadvantages, certainly. If you made this change, how could a lone bard possibly win against anyone who is deafened? I'll refrain from using the phrase "I win button" but honestly I see a change like this as making it virtually impossible for bards to win against anybody who preps with deafen. And the disadvantages are not very significant for solo non-mages.