Firstly, like said before. The shamans would, at most, hit you for a -2 to hit (as far as I know there are no cr9 shamans there) and that is much less crippling compared to the curses they like to hand out.
Continuing, that bane spell can still be removed by a single casting a bless or aid. Easy spells for cleric to slot, and bless is also readily found on clickies and 6pp potions.
Compare that to curse, which not only affects saves and skills but has twice the penalty. And to make it even more silly, curse can only be removed by either waiting, drink a pot worth 90pp or have a lv5 (?) cleric burn 20 sp on it. (compare to bless, that is mass and costs 10)
To summarize, nothing worse would happen with this change than without .
EDIT: Gaah, horrible necro!
Will teach me to not google "Useful divine spells", read for a bit and then leave the tab open...
Feel free to ridicule me. ^^