In particular, there are three things I wish to know: Reimu's level 2/3 spell, Mima's level 2/3 spell, and Chiyuri's boss attack.
Reimu's is aimed with a randomness factor (the orbs are aimed in your general direction in other words). I also found that it also generally tends to stay symmetrical if you're right in the center though. There isn't much else to this unfortunately.
Mima's is an entirely different case. As you may have noted, it fires from one corner. But, there are two distinct waves within it; circles and lines. It is most notable when the attack has just finished launching, like this:
Yellow marks circles. Red marks the lines. White cross marks the casting point (which appears to be random, not entirely sure). As Rank increase, the lines become closer to the first (outermost) circle.
Chiyuri's Boss Attack is... random. Very random. Except for the one where she shoots snowballs back and forth in a zig-zag-like pattern. A "safe zone" (not safespot) occurs in all positions diagonal relative to her position. In short; circles, more circles, random parallel (to some degree) cross-shaped walls. That's all I can see at this point.
The question is, how to deal with these? It is something I'm still looking at and testing.
Regardless, I do hope that helps.
LLS Lunatic run fully uploaded. Now waiting for processing.