There's no way it denies the normal card draw because it would then be the most broken card in the game. It'll act like burrowing mine in which case it doesn't actually increase the size of your opponents deck at all.
Summoned Ambush cards are 'summon a 4/4 Nerubian for your opponent. Draw a card'. (Source)
But the fact that Chrommagus + Burrowed Mine does not trigger 20 damage but 10 and puts a dead copy of burrowed mine that does nothing when played in the hand of the drawer probably indicate that the same thing will happen here, a dead copy in hand that if the player is crazy enough to play will most likely do nothing. (worth checking tho)
It will definitely make for some interesting mill synergy. It's not exactly like I envisioned it... I mean we can't just mill willy nilly or we will burn the Ambushes and get no value. Because of this it makes it a very good closer when there aren't a lot of cards left(very similar to Iron Juggernaut in that sense). But I also think it's good in the early game while you're waiting for combo pieces. I'm looking forward to playtesting it.
On average I don't burn more than 2-3 cards in one turn, so I think it will fit in regardless of burning a couple. The fact that some of their draws will randomly summon 4/4's for me is just too great with the chaos theory that is mill rogue.
Problem with putting this into a mill deck is that it has anti synergy. Since the card would be burned before activating it now counts as a real card as opposed to a fake one. So you are slowing down your own strategy. It could still be worth it though if the nerubians end up giving enough value through the game.
The win condition of Mill decks is not to burn the enemy cards (although this is a funny sideeffect) but to kill them with fatigue. Getting a lot of free nerubians while doing this is actually pretty funny. The only problem with this is that vanish puts them in your hand which is probably full anyway? But that that point you're probably winning because your deck is working so that's a first world problem. The nerubians might cover a "dry" turn when you don't draw more coldlights (it happens a lot...)
Funny how this is the first card I'm actually excited about because I love trolling ladder with mill rogue
Personally looking forward to building a control rogue that focuses around Nerubians. Im so sick of playing and seeing oil rogue that every time i see one or go to build a rogue deck, i dry heave until my stomach hurts.
People look at this and say wow rogues have no survivability, not useable. I however see rogue differently. They can stall and clear your board and screw you over in many different ways. Control will be a fun way to go and itll be hilarious when you start racking up nerubian threats.
I can't wait to physically witness the video of someone drawing all 3 immediately. Conversely, you could also play this and NEVER see a nerubian even in a prolonged control match. Still love the card for some reason and will definitely run with Burgle for shenannigans.