I would just like to inform you that "tapping your puppy" as you called it (Using Dark Pact) is a very inefficient way to get mana at level 80.
Life Tap at level 80 is actually like this
"Converts [1490 + SPI * 3] health into [1490 + SPI * 3] mana. Spirit increases quantity of health converted."

Which makes Life Tap>>>>Dark Pact, which isn't really that good.
Saves you GCD and therefore, ups your DPS.

I have yet to get this weapon, though it definitely does look very nice.

While Life Tap maybe >> Dark Pact, as a healer, nothing is more irksome than a lock tapping themselves to near death and then they expect to be healed back up by the team healer. That turns me into a mana battery for the lock.

Let him die next time. Maybe then the Lock will learn to throw a Life tap in at the end of his rotation and help keep a constant supply of mana.

@T

As Affliction, it's just poor mana management to need to tap more than once at a time, and flat out rude to expect a healer to keep you up. I always try to save tapping until either Haunt is about to come back, or there's a HoT on me - and if your health and mana are both low it usually seems better to switch tactics from optimal DPS rotation to old fashioned drain style until you're able to get both back up.