Lightning staff bomb build?

Amorpho

A quick question for all the mathematicians out there. Lightning staff grants 8% damage bonus to all AoE skills, I'd assume that includes soul tether and proxy det. So, on a bomb build that relies on these 2 skills, wouldn't a lightning staff be better than 2 swords?

Also, does might of the guild empower your ultimate or not?

Thanks for the help!