This deck is the most control heavy deck on the ladder right now. The idea behind it is to play some early minions then cycle and ramp up quickly to your late game.
The deck is favored vs Every deck IMO but here are its weaknesses.
The magic elixir does not matter at all in control matchups. You can play entire games without using even one charge. In agro matchups however the elixir is the largest decider of the outcome. Without it agro almost never has a turn 1 and you can keep up with agro, no problem. With it they can empty their hand by turn 5 and you lose to the momentum. This is the nr 1 source of my loses with this deck.
The second biggest source of my losses is Merric-at-Aswala. This card together with 1 minion on board and two chargers from raiding party presents a tempo swing that can be unmanageable. The effect of Merric-at-Aswala is random but for the most part extremely powerful. The battlemage can go from having 2 power on board on turn six to having 20 power on board with three attacking minions on turn 7. This card needs to have its cost raised . Other then that battlemage is a fun matchup that this deck is slightly favored against.

That’s it for the weaknesses. The strength of the deck is that its the most powerful control deck on the ladder. When I play this deck I sit back until my opponent leaves or I kill my opponent when I have lethal on board. Sometimes I wait even though I have lethal since you don’t know what prophecies might trigger. In general you want to heal up with snaketooth and attack on the same turn to make sure there can be no swingturn. There are some matchups where it is best to attack your opponent especially vs.. battlemage since they can get past your taunts with atromancers and spells.
Battlemages also suck at defending so its OK to put them on the defense.

So why wabbajack ? I got it in a pack and felt like playing it for fun. After using it a lot I would not replaces it for anything except maybe a forth shadowfen priest. The card is used to deal with huge threats and you can use it to buff your small minions to build a board. Its prime targets are blood magic lords and the iron atronarc.

I only use snaketooth necklaces and BML to heal. With the amount of carddraw you have you are likely to draw at least one snaketoothe during the course of a agro game.

Why not use nightshadow ? This card sucks at healing and is one of the first cards I removed from my netdeck. It has breakthrough and draws cards for your opponent with it. You might not have a unit to attack and it can easily be silenced and then you are left with a big body that is useless to you.
If you want more healing put in restless templar. They are only weak to silence and your opponent not having a board. However IMO they are to slow in the current meta so I replaced them with card draw.

Here is a tip that not everyone knows. You can use blood magic lord to sacrifice your own unit when you play him. You need to have a full lane to do this. The sacrifice counts as a kill and gives you two cards. This gives you synergy with bone colossus witch you can play if you are missing some legendaries.
I got to rank 3 legendary with this deck. Want proof ? Watch my stream https://www.twitch.tv/nikicahs . I play this deck all the time since its the only one I have cards for. That’s all I can think to say on top of my head. Feel free to ask me stuff though.