Based on similarity to the summer water gun event, it's likely that the last four opponents in the new rogue nation event drop a valuable SSR Evo card with about a 0.2% probability. In the water gun event, I got 12 such SSR Evo cards in 5600 attempts, which is enough to get a pretty good estimate of the probability even when it's that low.

The last two opponents this time are rather annoying, as they're very strong corsair mobs that do massive reflect damage. My usual PVE group that cleared the entire campaign loses outright to both of them, and to beat them, I have to swap some parts and have something inappropriate for the warlords. The other two are much easier to defeat.