Hearthpwn

1) Shadowflame is almost mandatory card it any control warlock deck. And there is none here.
2) Not enough reliable dragons for 2 Blackwing Corruptors. Why reliable? Because you really want to play Twilight Drakes on earlier turns and Azures for spellpower/rotation.
3) 2 owls is overkill. Silence is always good, but killing stuff is more important. 

I disagree on the shadow flame being MANDATORY, amazing card but not necessary in a MalyLock deck, Although he may want to add another hellfire. One AoE is not enough. I run 2 corruptors but that's just personal preference, they come in handy. And 2 owls is overkill for sure.

Any idea of how to replace Blackrock mountain Naxxramas cards?

Unfortunately no replacement for Blackwing Corruptor