Yuka's flower walls work amazingly well for walling in the AI. No matter how broken Shiki likes to be when it comes to dodging, she can't possibly dodge a solid flower wall without bombing, which can mean the end of that last half orb.
This works... once in a blue moon. Yuka's "solid" walls aren't really that solid. You can get the "Icicle effect" with two coming at the same time and at the same speed next to each other exactly on top of the AI's hitbox, but I wouldn't count on it - I still prefer to not care about what's happening on the other side of the screen and just hang on for just over three minutes which is how much non-first-round story mode lunatic Shiki usually lasts against a character that doesn't throw any AI-breakers at her at the exact right time.
Yuka
can (as Reimu
will) eventually give you a quick win, but can you say it's something you can count on happening? No, you can't, and advice like this only adds up the frustration because it further adds luck as an element, and when you devise a luck-based strategy, people start to expect possible but very unlikely things to happen all the time, and then everyone starts to bitch about how the game is unfair because Reimu's balls are supposed to obliterate Shiki and it didn't happen, etc etc etc.
The only thing you
can count on to an extent is the magical three-minute mark (that's the timer for lunatic, I don't remember how long it takes on lower difficulties - probably more since there's a lot less bullets for the AI to ram into as well) - and even that can go down the drain if you take the "stop shooting" route, though I haven't tested it extensively yet because it's another unreliable tactic which just further adds variation. It's "good" if you're trying to punch above your weight; it's
bad if you want reliability.
And speed is hardly as big a deal as you seem to make it out to be. If this computer could handle it, I'd go fight Lunatic Aya in match play with Yuka right now to prove it, too.
Most of Aya's attacks are
streamable. She's one of the easiest characters to survive against, even if she's very likely to get you once in story mode anyway because she'll survive long as well in the first round. A "regular" good PoFV run will see one death each at stages 6, 7 and 8 with any character, and be decided at how well the character you're playing with deals with Shikieiki. No one is complaining about Aya taking all of their lives.
Picture this: I tried 1cc'ing lunatic with Yuka for a long time, often failing after arriving at Shiki with four spare lives; then I tried Reimu for a while, and got my 1cc with
much difficulty, and still can't do it reliably enough to
expect to win every time I try; but I can 1cc lunatic about 80% of the time (if not more) with Mystia, Cirno or Marisa, who are the fastest non-broken characters.
tl;dr;
/rant
