Hearthpwn

I played this exclusively (little variations) down to Diamond 2 but fell back to 5 yesterday (horrible day) as I played a TON of rogues and struggle mightily with them.  Any advice (besides to drop dead from priest haters) for playing rogue?  I accepted that hunter and rogue are tough matchups for priest and made my climb on other classes, but seems like they were all I faced yesterday.  

murozond is key against rouge,play it after they play the card that give them 3 cards 0 mana.

CAn murazond be replaced or is he just too unique?

He helps with breath and for some big turns from opponents, but you can go without him as he's possible to get from invoking Galakrond.  He's super useful, in mirror matches too. Anyway, in my experience I have him in, but not essential.

Serious question, what is Soul Mirror supposed to tech against?

It helps clear large boards in general. In some situations you could use it on minions such as Priestess of Fury or Kalecgos that will live and let you use their abilities on the same turn.

true, except kalecgos, soul mirror would be the first spell of your turn, but you'd have a 4/8 kalecgos on board which is nice

What would you recommend as a replacement for Madame Lazul ?

You could replace maybe it by Vulpera Scoundrel 

this deck got me to legend today

Replacement for Fate Weaver? 

I would try Holy Nova