In this build I'd say that
Mikaeus, the Unhallowed wouldn't be terrible, it doesn't give all of your creatures undying simply because you've got a decent number of humans, but if you can give Grave Titan or Thrun Undying that's pretty sick. Glissa is a cool utility just because she kills pretty much everything without even having to try but you don't really have enough artifacts to make it worthwhile since Equipment don't go to the graveyard.
If you have both of them it's 100% worthwhile to take out the
Bitterheart Witchs for them, First Strike and deathtouch for 3 mana is way better than regular deathtouch for 5, and Mikaeus is unblockable unless your oppponent has a black or artifact creature and if they're playing a humans deck it's just insane, the problem with Bitterheart Witch is that you don't have any curses in the deck, if you have some then she's pretty cool, you can kill their best guy by blocking then go get curses to hurt your opponent worse