Arr. Scarrrlet Meister be a scurvy dog of an attack, an' no mistake.
... :V
Anyway, I've beaten it numerous times getting hit once and clearing the rest. As far as I can see, I just need to survive three consecutive waves and I'm in the clear. I've survived two before... I think I have a general strategy down for the easiest way to clear it which kind of relies on you controlling, to a degree, where Remilia moves. Admittedly I've almost always been fighting it at a fairly low rank, but still. It honestly feels less difficult than something like, say, Vengeful Cat's Erratic Step. It's difficult but it plays out approximately the same each time and though it's dense and fast, you only have to really watch one wave at a time rather than trying to read a gigantic clusterfuck of circles from every direction. Difficult, but fair. I'm guessing its reputation is from the high/max rank version, which I don't think I've seen yet. A cap might not that much longer... most of my deaths are seemingly to do with me panicking and forgetting which direction I should be moving in.
Also, I tried a run of UFO Lunatic Stage 6 earlier. I have yet to capture any spell card on that level; I died on every one of her last four cards with the life bar at around a few pixels remaining. <_<