With Tachyon Lance, I purposefully fire it at shields because if it has some hard flux, some of it is getting through. Also, if I use two or four on Paragon, the burst damage is enough to flux cap some of the enemies. I want lances firing, and crossfire is good. The only time lance is bad is if target has no hard flux and can easily tank a lance strike.
Tachyon Lance is fine as an general-purpose assault weapon.
Phase Lance might be the same way against smaller ships, except for no shield piercing. Aside from being poor-man's AM Blaster for Harbinger, Phase Lance is more of a PD weapon, anti-frigate instead of anti-missile.