Since the other thread regarding this topic was deleted (or was it just moved? I can't find it) I'm starting another one.
Wail on a bard is a useless spell. Bards have no enhancements to improve their necromancy DC. Unlike wizards they have no spare feats to use to increase their necromancy DC. They cast at max spell level 6 instead of 9 like wizards/sorcs, and they have no access to other necromancy spells for debuffing, like enervate, energy drain, circle of death and symbol of death.
Wail of the banshee on a bard will be worthless in anything above epic casual. This is an exceptionally poor choice of spell for a caster bard to get, and we all know that bards are in dire need of additional spells.
Please consider replacing this spell with "Mass Hold Monster". This is a spell that bards would actually be able to cast effectively, and may possibly make caster bards useful again (though lets not get ahead of ourselves here, they still can't damage anything!) Increasing the spell level to level 9 instead of 6 might also be necessary to make caster bards competitive, but even just giving them the spell would be a great start.