The CS rotation is VERY strict in optimal performance. You ALWAYS BT before CS, and go BT-CS-RB-BT-RB-RB with a heroic leap+3-4 HS in there. If you have 2 RB when BT is off CD (which should ONLY happen from 2p proc) than you'd RB-BT-CS-RB-BT-RB-RB.
If you aren't enraged before going into CS phase, you're doing something wrong. If you don't have rage going into a CS phase, you're doing something wrong. If you don't have 1 RB stack before going into CS phase, you're doing something wrong.
Here is how I'd handle a less than perfect phase, where I have 5 seconds on my RB charge, am not enraged, and neither the BT nor CS crit. I'd hit Brage here, RB, BT, RB, RB. That way all 3 RBs are enraged, and I'm guaranteed at least 2 RBs, without ever risking an overwrite of a RB stack. Of course if I'm really unlucky and that 2nd BT doesn't crit, I'm just SOL. Nothing you can do about that. Hit 2 proced WS if you can in that case.
You're going to keep CS on ~21 second CD, although I've heard arguments for 22.5 (Not sure if that holds up anymore w/ higher crit haven't looked.) Basically, BT-CS-RB-BT-RB-RB-BT-RB-pWS/IV/HT-BT etc. Remember, if the first BT after CS ends crits, you can use that RB right away (while enraged) since there is no way you can keep it for the next CS phase.
Execute CS usage is just BT-CS-X-X-X-X-RB-BT-RB-RB (specially after you have no more CDs up).