Dark Knight MP gain percentages for each skill

[Lyth]

Piety is no longer a racial stat. Please refer to Patch Notes 4.0: "The starting attributes of all races have been changed." You can find the current list here. Your base MP is determined by your job and character level, with healers exclusively having the ability to slot additional MP with their secondary stat choices. Every DRK at level 70 will have 9480 MP.

Rather than looking at MP gains and costs, it's better to conceptualise things as a common currency, or potency. The net value of 1 DA is 140 potency in Grit and 168 potency out of it. The net value of a Bloodspiller is 185 potency in Grit (on average) and 165 potency out of it.

Looking at combo potencies, we have:

HS [150] + SyS [250 + 0.5 DA/1 DA] + SE [300 + 10 blood]

If you just look at the potencies themselves, you have 233 potency/GCD in Grit, and 282 potency/GCD out of Grit. If you include the value of the resources themselves, you have:

HS [1.2(150)] + SyS [1.2(250) + (168)/2] + SE [1.2(300) + (165)/5] out of Grit, which works out to be 326 effective potency/GCD.
HS [150] + SyS [250 + 140] + SE [300 + (185)/5] in Grit, which works out to be 292 effective potency/GCD.

So when you account for extra resource gains from Syphon Strike in Grit, the effective potency difference is narrower, but you still lose about 34 potency on average for each GCD combo action that you use in Grit. In addition, it costs you 1 GCD and 0.75 DA to swap into Grit, which is worth 452 potency. Stance dancing on DRK is a fairly expensive ordeal.