I've noticed that behavior on Cut to the Chase as well. I suspect a double hit on latency may be the cause. I know my timer mod seems to have a delay on refreshing SnD after hitting envenom, so I think it's the timer that's off by just enough to make trying to refresh SnD via CttC with <1s a dicey affair at best. I usually aim to refresh SnD at 3s or less on the off chance the Envenom gets dodged so that usually avoids the problem.

Killing Spree does not work well with 'phased' content; you may get an 'invalid target' error. After first noticing this error in the Kalecgos fight I've made an effort to use it whenever phased. Sometimes it will work but many times not. I believe it has to do with whether or not the mob has been phased into your environment or if you have been phased to it's environment.

A good example of this is during a quest in Icecrown (Get the Key - Quest - World of Warcraft) where the quest causes the target NPC to phase into your realm. He's been phased in so you can kill him for the quest and Killing Spree will not work on him. Other players can see and interact with you but not him.

Back to the Kalecgos fight, I assume Kalecgos is native to the player environment and Sathrovar is not. Using my previous assumption that would mean Killing Spree would work on Kalecgos but not on Sathrovar which is the case.

Assuming Blizzard phases the least number of players/NPCs possible, Killing Spree may or may not work in phased content depending on who/what was moved and to where. In cases of single or few NPCs phasing in, it is unlikely that Killing Spree will work as they are not 'native' and you are not the one who moved.

Edit to further clarify:
There is another series of quest in Icecrown where you must retrieve body parts of a fallen NPC near the Fleshworks. In this case the player is phased and Killing Spree is usable in this case.

I've had savage combat debuff consumed after only one hit with a physical attack or at least disappear, when using only wound poison. The savage combat debuff hasn't dropped off when using deadly poison in conjunction with wound poison or by itself.

I haven't yet specced into Cut to the Chase, so I'm not sure if it's the same behavior, but based on how you described it, I think the same bug is also affecting Deadly Brew. It makes sense that both of these talents would be coded similarly so I thought it would be relevant to mention this.

With Deadly Brew, *EVERY* time I apply Wound Poison, the Crippling Poison debuff that is procced from Deadly Brew takes an extra ~1 second or so to apply. You can even watch the mob's debuffs and see the Wound Poison debuff appear upwards of a full second before the Crippling Poison debuff appears. And I play with as low as a 19ms ping on my realm.

It's clearly not just a matter of latency, either, because you can visually SEE when the Crippling Poison effect applies to a moving enemy player (because he starts to move slowly). For example, if I use Shiv to apply Crippling Poison (without Deadly Brew) to a player that rides by on a mount, he will be slowed *instantly* and won't even be able to leave melee range most of the time. On the other hand, if I use Shiv to apply Wound Poison (with Deadly Brew to apply Crippling Poison also), the player will always continue moving at full speed for approximately ~1 second as earlier mentioned, and always will be well outside of melee range by the time he gets snared. I then have to run toward him for a bit to catch up.

Any theories on why this is happening?