I'm an old Warlock player and it's in my blood to cast as many DoTs as possible while letting the 5-second rule do its thing. Vampiric Touch costs 400 mana, but 5% of all shadow damage done while the debuff is up is returned to you as mana as well.
Vampiric Touch at level 64 with 311 spell damage, Misery (+5%), Shadowform (+15%) and two stacked Shadow Weaving (Vampiric Touch and Shadow Word: Pain - 4%), does 1258 damage.
5% of that is 62.9 mana returned.
Shadow Word: Pain at level 64 with the same damage enhancing factors, does 2198 damage.
5% of that is 109.9 mana returned.
After letting the DoTs do their thing (but before Shadow Weaving fades), I almost always finish the fight with Mind Blast followed by Shadow Word: Death. Normally the mob would have more than two Shadow Weavings on the final spell, but I'll roll with two because I'm lazy.
Mind Blast will hit for an average of 958 and crit for an average of 1467 damage.
5% of that is 47.9 or 73.4 mana returned.
Shadow Word: Death will hit for an average of 855 and crit for an average of 1293 damage with all those debuffs on.
5% of that is 42.8 or 64.7 mana returned.
So by casting a spell that costs 400 mana, I get another 1258 damage done and 314.5 health returned through Vampiric Embrace. And since the mana return total is 263.5, the actual cost of Vampiric Touch is only 136.5 mana.
136.5 mana and 1258 damage done gives it a DPM ratio of 9.2. In comparison, Mind Flay, which is the most damage to mana efficient spell we have, has 4.8 with the same debuffs applied.
And you get 314.5 health from it as well, which puts the HPM ratio around 2.3, while Flash Heal at that same level with 350 healing has a ratio of 3.
Holy crap, that's a lot of numbers. I hope I got everything right. Of course, numbers may vary due to resists and crits. Usually either Mind Blast or Death will crit, making the mana and health return even greater. I also use Inner Focus to make Pain or Touch free of charge every 3 minutes. Plus I was lucky and got
Auslese's Light Channeler one night. By rotating between Inner Focus and the trinket every 1.5 minut, the mana saved is amazing. Plus I use the
Vengeance of the Illidari every few pulls to shorten the fight and increase all values returned through the spells.
If you're wondering how I found my averages and all that jazz, I'm using
DrDamage, an addon which puts a lot of useful (and useless) crap in the tooltip when you hover a spell. And it updates directly, so if you hover Mind Blast and the target is affected by Shadow Weaving, the tooltip will update to show the math with those extra 2% added. Very handy.
Edit: teacake, I think I'd get Meditation before Vampiric Touch pre-60, though. Meditation is 30% mana regen during combat. And the lost damage via Vampiric Touch can be made up for by going Wand Specialization. Hehe. Okay, maybe not. But still, at lower levels I found myself wanding a lot while letting Pain and Vampiric Embrace adding to the survivability. Make sure you replace your Psychic Scream on your actionbar with the first rank. While leveling you rarely need to fear more than two targets anyway. Any higher rank is just a waste of mana.
Meh, it's been a while since I was leveling in Azeroth.
Edited, May 22nd 2008 12:49am by Mazra