Runic power and rune regeneration come first, because they are the DKs mane resource.
Blood Tap, Runic Empowerment, Runic Corruption, Sudden Doom, Glyph of Death's Embrace need to be fixed first in order for the DK to work as intended. And if a DK stacks 200k healing absorb that means that the DK is skilled and that you need to l2p, If you let a DK stack that many necros on you then you can quit WoW PVP or just Alt-F4 when ever you see a DK. It is very hard to do that when DK's rune regeneration abilities are bugged.
And the absorb for 1 hit is 30-50k so for 200k stack the DK needs at least 4 death runes leaving the DK with no runes and no way to continue the stack. The DK can continuously create death runes but in PVP situations the DK can't use all of his death runes on necrotic strikes, and those death runes fail because the rune regeneration is bugged and you never know if a death rune going to be available or not, even with Blood Tap. Runic Empowerment and Corruption are completely useless when it comes to necrotic stacking.