Originally Posted by
Rustjive
Your opener is wrong. You precast UA thinking that you get to get some free cast time before the pull, when in fact you are looking at it wrong. You might ENTER COMBAT when the boss is pulled, but your personal fight begins during your pre-pot. As soon as you pre-pot, every action you take is taking up active time on the potion. Not putting up Corruption during your opener unlike every other Warlock is just a plain DPS loss. You might save a shard by applying Agony/UA manually, but you lose 2-3 ticks of possible Shadow Trance, and then you lose ticks of the Agony you manual cast when you SB:SS so soon afterwards.
In addition, Shards being 'wasted' is just...whatever. You only need enough Shards to Haunt until your initial buffed DoTs get replaced - because you are pooling Shards for the next DS there is a good chance that any excess Shards you accumulate only go into Haunting weak, non-buffed DoTs. If the choice is 2 GCDs worth of MG on strong DoTs or a Haunt on weak ones, the choice is very clear.
The opener that I use is this: Pre-pot, DS/BF, SB:SS to pull, Haunt, MG until 1.5s left on Haunt, Haunt, Fel Flame, MG until < 1s left on BF, SB:SS, MG, Haunt, etc. At my haste levels I almost always have enough shards to have Haunt-perma during my buffed Agony.