TsKIB OTs-12 Tiss – ★★★ Assault Rifle
"Are you THAT short on ARs or need cheap equipment that badly?"
You get much better ARs from story events, and there's only so much that you actually need. If you need a cheap AR and already have FNC though I guess she can be useful.
Can reach 115 ROF with her buff alone, which is unfortunately 1 less than the 12 frame breakpoint. Has terrible base FP, but mitigated slightly by equipments. While her tiles are good for position 7, most position 7 OT-SMGs give ROF as formation buffs, which doesn't benefit her.
While theoretically equal to FNC, she has no armor busting capabilities (even at early game) with very little significant advantages (ARs don't do enough damage that doing more hits will significantly improve performance). Might even fall off later in the game if more enemies gain light armor. If choosing only one between FNC and OTs-12 (and nobody else), FNC should be prioritized first.