Originally Posted by
Farseer
The reason we need Rupture is not really the dps it does, but the energy it gives us in combination with the poison DoT. Envenom does more damage than Rupture, especially if it crits. That's why you shouldn't be casting Rupture during the first 8 seconds of SR + Vendetta. What your guildmate does is fine, I suggest you open with:
Mut > Rupture at 5cp > mut until 5 cp > maybe pool some energy for a few seconds > SR + Vendetta > Envenom > mut until 5 cp > Envenom.
The 5 cp Envenom you cast after SR+V will be a crit and you should be able to get at least one extra Envenom before the first 8 seconds are over. Depending on the amount of crits you get it might be a close call on refreshing Rupture. It usually falls off right after the first 8 seconds of of SR so you have to keep an eye on that.
For the next SR + Vendettas, try to save up 5cp + 3-5 Anticipation charges (assuming you have that talent, which I strongly suggest) so you can cast 2 Envenoms or Envenom > Mutilate > Envenom right after popping SR+V. If you're lucky with crits and have pooled energy you might even squeeze in 3 Envenoms in the first 8 seconds of SR, and this is good for your dps.
I think if you get this opening right (a lot of it is RNG unless you stacked crit like mad) it'll do wonders for your burst and consequently your overall dps. A good start burst makes all the difference. Like someone else pointed out, in your normal rotation you'll not want to Envenom immediately when you have 5 cp, but wait till you have (almost) energy to cast two mutilates. Rupture uptime HAS to be 100% on a single target fight without interruptions. If you let that fall off for 1+ seconds you'll lose a lot of energy and that will punch a hole in your rotation.
Something I personally do is, when I have 5 cp + some energy pooled, and no Envenom buff while Rupture is within 5-8 seconds of falling off, I go for Envenom to profit from the buff and then spam mutilate so I can update Rupture at the very last second. This means I can still refresh Rupture right before it falling off whilst enjoying the Envenom damage buff to the Mutilates I've cast, and if I'm lucky with crits I can even get another mutilate (so 2-3 combo points) before the Envenom buff ends. This way I usually only have to cast one Mutilate without the Envenom buff to reach 5 cp again, then pool some energy and cast Envenom again.
I think to really optimize the rotation and Envenom uptime, you'll need to stack a certain amount of crit. I'm at 28% crit unbuffed atm (669 ilevel), 1 weapon with crit enchant and 1 with mastery (though I'm thinking about switching to double crit). I assume your ilevel is higher than mine so if you go pure crit you might end up often having to clip your envenom buff because of generating too many combo points. I suggest you take a look at how your guild mate has enchanted his gear, and which stats he has, and reevaluate your own gems/enchant.