My girls are heavily underleveled, I'm running out of buckets, my fuel count is below 7k, I got 4 days left and I can only spend about 3 hours a day but...I'll continue to try and clear E-6 on Hard!!
got my Roma after around 30 tries of sorties on E-6
231 sorties, spread over several days. First 21 sorties were at the boss node, before I shifted to node M for 20 sorties, then stayed at node K for the rest of my farming. RNG was ridiculously harsh with the drops, I assure you, with many instances of Perfect S giving nothing and, at one point, FIVE Mutsus within a 30-run stretch. Ugh.
I feel your pain. But don't worry, I'm sure they'll make Roma buildable or drop from next event. Don't expect her to come easy through. She'll probably harder to craft than Bismark, Taihou and Yamato put together.