Hi everyone.
Sorry if my English is not so extense.
Dark Bridge Grants bonus is inferior than Mercurius Rod.
In my opinion Megid is not a common spell to kill enemies. I ussually go Foie, Zonde, Barta type techniques.
FOrces are intended to make spells. From what I see here is that Dark Flow & Dark Meteor are killing machines (included Bosses).
So why not make it a great weapon against bosses. The best technique for bosses is Simple Techs (some exceptions like Dal Ra Lie, Barba Ray, etc) if i am correct (Example Foie vs Sil dragon greater than RAfoie)
A good boost for Simple Techs (40-50%) + TP Reduction will make it a tempting option for FOrces.
Using as reference for the Simple Tech Bonus (Club Laconium 40% Foie, Mace Adaman 40% Barta, Club Zumiuran 40% Zonde). And as special of this weapon maybe something based in Techniques. Or nullifying randomly enemy techniques or hits.
Well this is my opinion about giving a great bonus for Dark Bridge and making this Dark weapon more desirable for players. Have a nice day