To build CP outside CDs, use Backstab as the primary CP builder, and use Hemo every 24sec for keeping the bleed from the glyph up.
Generally if you are really low on energy ( < 30) you wait for some HaT proc untill you are at ~70, then depending on your CP you Backstab once more or not. IE:
70 energy, 4 CP -> Wait for a HaT proc and go into your finisher
70 energy 3 CP -> Use CP builder (BS or Hemo) and wait for HaT to fill the 5th CP
Generally, if you are low on CP and high on energy, go for one or two CP builder. If you are low on energy, wait for HaT proc. But this is a lot of practice.
In case you are at 3 CP and low on energy ( < 30) wait for HaT proc to fill untill 5th (if not energy capping ofc)
In case you are at 3 CP and high on energy ( > 70), go for CP builder and wait for HaT proc and go directly into evisc.
Sub "rotation" takes a lot of pratice, but with enough practice you can achieve good numbers (I managed to do 32k DPS on Baleroc with an average ilvl of 377, everything depends how used to the spec you are)
Also, as it has not been mentionned in the OP, I recommend this addon for all PvE Sub rogues:
http://wow.curse.com/downloads/wow-a...hatracker.aspx
What it basicaly does is tracking the ICD of HaT, so that you know exactly in a raid environment (due to the very high number of crits at any given time) when to expect a HaT proc and you can time your attacks and/or empty your CP bar right before a HaT proc. I was the one who proposed such an addon to Brusalk who coded it, and for having used it the whole time I raid as Sub, it defintly helps a lot to manage your CP generation and help not wasting any HaT proc. This addon should be a must have for any real PvE Sub rogue.