Shiki certainly did get toned down in this game. Her special moves just aren't what they used to be, and I'm greatly disappointed by the absence of her excellent command moves from SvC Chaos (f+ A and f+ B are no more). However, she's still reasonably powerful, with a variety of moves and a unique fighting style.
b/n/f+ CD when up close
Basic throw. Moving on...
dp+ A/B/C (can also be done in mid-air)
Shiki spins upward with her swords slicing through the air. The same move from SvC Chaos, except that this move now has some horizontal range (which makes it a bit riskier if blocked). And sadly, this move seems to have less priority than in SvC Chaos.
Shiki dashes forward in a blur, and slashes her swords when she reappears. Hits low, obviously. The same move from SvC Chaos, except that she moves forward a bit when she slashes.
during Tsuyu Harai, A/B/C (might be specifically the button you used for Tsuyu Harai)
Shiki jumps in the air and does a backflip while swiping her swords upward. The same move from SvC Chaos, except that she can now follow up this move with other moves. If I keep mashing qcb+ A/B/C over and over again during Tsuyu Harai, I find that Shizuku Gari, Ten Hourin, and Kourin will come out in sequence. Ten Hourin does not seem to connect, but Kourin does.
Shiki hops forward while doing a front flip, swinging her leg downward. This move is an overhead. Unlike in SvC Chaos, Shiki only has the overhead knockdown version of this move in NBC.
hcb,f+ D when up close
Shiki grabs the opponent and appears to be casting a spell. In addition to inflicting damage, this move causes the opponent's directions to be reversed. This effect will last until Shiki is hit or the opponent switches with his/her partner. Basically the same move from SvC Chaos.
mid-air qcb+ A/B/C
Shiki flies downward while slashing in front of her. I noticed that, compared to SvC Chaos, this move has significantly shorter startup time in NBC, although the move itself seems to be slower. Also, whenever I played Shiki, I found that mid-air qcf+ A/B/C also works. However, I'd still do qcb just to be on the safe side.
Shiki disappears in a flash of light, and reappears somewhere else on the screen. Same concept from SvC Chaos, except that the C and D buttons make her reappear in the air (kinda like Strider Hiryu from the Marvel vs. Capcom games). Basic teleport move.
Shiki dashes forward very quickly. If this move connects, she slashes the opponent multiple times and finishes it off with a particularly damaging Ten Hourin. This is the exact same move from SvC Chaos. The A-version of this move has the least startup time, while the C-version has the most. This move consumes 1 Super Bar.
Shiki dashes forward very quickly. If this move connects, she jumps onto the opponent and slashes his/her neck. Then Shiki, not to be outdone by Hotaru Futaba, does her own version of the "orgasm super" and sits on top of the supine opponent. A burst of energy occurs and Shiki's life is restored at the expense of the opponent's. This is the exact same move from SvC Chaos. I've noticed that she doesn't regain much yellow life, but the amount of red life she regains is substantial. Also, I can't say for sure, but I think Shiki regains a lot more yellow life from this move if her partner is defeated. This move consumes 2 Super Bars.
Despite the loss of Shiki's command moves, she still has a super combo that's fairly easy to do:
jumping D, crouching A, crouching B (2 hits), qcb,hcf+ A/D
The cool thing about this combo is that you can start from any point in this combo (except the qcb,hcf+ A/D, obviously) and the rest will still connect.