another HD combo I use in the corner when I don't have much meter is (IE not enough to do a MC at the end):
St. C, f+A,A xx qcb+BC (activates HD with special) (2 hits) [HDC] dp+C | (qcb+B [HDC] dp+C)xN | qcb+B, qcf hcb+A/+AC.
I'm not positive on the number of loops of (qcb+B [HDC] dp+C) you can do before you run out of HD. I think its 3 or 4. If you end with EX ya otome the combo does 780. I also can't currently remember if you can add a qcb+A at the end, before the ya otome, but if so, it might add a couple more damage.
It's pretty much a variation on the already-known 1000+ damage HD combo without using the dp+A [HDC] qcb+B [HDC] dp+C starter to get into the qcb+B/dp+C loop (which I personally have trouble hitting consistently after st. C df. C [HD activate] st. C df. C starter), and without using a max cancel at the end.