One of the things Ive been reading about on various blogs/forums is the extra threat from improved Vamp Embrace – I try and use it as often as possible because it heals me when i do Shadow Word Death and get damage backlash – it helps my group by working almost like a Hot on bosses that do Aoe, however some shadow Priests recommend that you lose improved vamp embrace on the talent tree because of the agro.
But there are some fights where I shouldn’t theoretically be taking damage. Eg in the Trash in gruul’s lairso in order to reduce my argo I left VE off untill I was Using SWD – It seems to work – only got a random cleave once.
The Gruuls fight when I was in CD we used to mark the healers so that when we are trying to get to a safe place for shatter we don’t land ontop of a healer. VE is important for my group in this fight because of Shatter and the Rock falls. It also means Im free-er to Shadow Word Death more often because in between avoiding/taking damage you can DPS to your hearts content due to the high argo on the tank, I was managing my self preservation skills quite well in the last Gruuls fight
Runaway from everyone and against a wall for shatter – Sheild and bandage / VE DPS / Healthstone during any Rockfall or shatter Damage. I was sweet. The VE is good for my group, aiding them in their self healing while the healers concentrate on the Tank – this worked well, untill Gruul was down to about 2% and some of the not so careful DPS had dropped off, shatter is a dangerous one, if you are standing too close to one or multiple people the damage is amplified, I had fallen back to a wall for Shatter protection and a mage blinks right into me. Just in time for the Shatter to hit. Luckily he died. Not Me. I was fully healed, but just lost 4.5 K because of his proximity.
The argument from the raid leaders are that we should be at a level now ( or the healers at such a level) in that they do not need ‘help’ from VE and for the most is just overhealing, and I agree to a point, but I don’t believe I should rely on a healer to heal me when I’ve just crited myself for 3k Damage on a shadow word death, especially when VE in a Mana intensive/Tank requiring heal encounter and its each man keeping himself up, then VE is Very Nice. No way is it leaving my talent tree.,
Says My group on 1st Attempt on Tidewalker the other day” Awesome healing! Especially after some of that Aoe. Takes less pressure on the healers. and that os a good thing,
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Pugnacious Priest's Warcraft Blog 
Hey Zah,
I’m no seasoned veteran of the shadow priest world by any means, but i specced it for a laugh the other day and i’m looking at 1150sd with an elixir and oils. In my experience not picking up imp VE allowed me to essentially keep all my spells on cooldown fairly constantly without hitting the aggro ceiling.
If you have the means, certainly try both and I’m sure you’ll see a difference.
Cheers
Pat
Imp VE does help w/ the heals when needed as you cited but eventually you may want to spec out of it as you acquire more spell dmg. since you will definitely be generating a lot more threat. Besides, more spell dmg. means more “ghetto heals” anyway so you can safely move those 2 points elsewhere to maximize dps.