I am sorry, but playing Archer without having the Soul Crystal equipped is just NOT optimal. Yes you may be able to gain access to a wider variety of Cross-Class abilities, but the entire reason people want Archer's in End-Game Content is because of the Bard Songs, not necessarily because of their DPS Output...
DPS Archer maximizing cross-class abilities (end-game theory)
Guide in 'Disciples of War' published by rhkim85, Apr 4, 2015.
A Guide for endgame Bards for how to maximize their DPS and a look at choosing cross-class skills.