Here are some Class Death Knights of WoW and you can buy the cheapest World of Warcraft gold:
Raziel if you ever come back here to see if you got a answer here is one.

Ghoul- yes the ravenous dead and glyph should stack to offer your pet +80% stm and strength.

Runetap- from what you have seen, it offers you 110% of your health back, but you haven't used runetap since.

level 62(WoW powerleveling). Even if it doens't stack, you could gain both for the raid heal.

Necrosis- Necrosis does shadow damage when you use a auto attack. Auto attacks are just your weapon stricking. Nothing are special about it.

Impurity- With the impurity it helps with spells, you have done weapon damage. For exp heart strike, plague strike and obliterate. It is almost a must for deathknights in unholy. That is the content! See you next time.