Shingen is next best soul after d'art for thunder for higher burst builds, since thunder can be super fast with building gauge like Baal U, Brahma, Marduk, etc.. and iirc, shingen gets a buff in a future update? something like that.
Hercules is better for a team like wind or fire which relies heavily on buffs and nuke damage... tho i'm not quite sure.

i've just seen everyone switch out D'art for Shingen after getting Baal U.