***TRIALS RESPONSE***In my opinion, the deck in the OP is the best version. The main goal of this deck is to get poison out as fast as possible, not to stall and kill your opponent's creatures. Using shields and CC lead the deck down those paths, slowing the deck down and distracting the focus from getting quick poison. The first has a good foundation, however it needs improvements. Using other modifications previously posted as well as these that I am suggesting, you should be able to maximize the output of this deck.
First, it does not have enough Death quanta. The quick and easy fix to this is to change the mark to Darkness and change the Darkness Pends into Death Pillars/Pends. Since you do not need as much Darkness quanta as you did Death quanta, some of the Pends can be replaced by Death Pillars to give you more Death quanta, which is the main quanta focus of the deck. You will still be able to generate enough Darkness quanta with the mark and Pends generating every other turn.
Second, 4 Steals is a little overkill, and with the shift to Death Pillars/Pends, quanta for the Steals might be a little scarce. So, you can take 2 of the Steals out and replace them with any cards you want, whether it be Arsenics, shields, Poisons, or more creatures. With the 2 Steals left you will still be able to deal with pesky shields and weapons that can stop the attacks of the Deathstalkers. I personally would add 2 Arsenics here because they are a reliable source of poison and can make a huge impact on the game if they are drawn and played early.
With all these modifications your deck should look something like this:
Hover over cards for details, click for permalink
52g 52g 52g 52g 52g 52g 52g 52q 52q 52t 52t 52t 52t 52t 52u 52u 52u 52u 52u 52u 542 542 542 542 5up 5up 5uq 5uq 7ta 7ta 8pt
I hope I was able to further help speed up this deck and make it more effective as an ai3 grinder.