Please, remove instant shield.

I completely disagree.

The shield system is one of the things that make this game so unique and fun. You want to talk too much random? See Hearthstone. 

This system is just the perfect mix of strategy and luck which makes for insane "woohoo" or "F*******ck* moments. 

I love it and hope it never changes!

I agree that the instant shield (Mega block) is far too random and should be removed. The free heropower tricks you get are so powerful that they often decide the game. But I think the random 1-3 notch shield charge is fine, because you can play around the limited randomness and the built in catchup mechanism of the shield makes the game more interesting.

As for the Hearthstone comparison:  Blizzard has in the past designed cards that are too random (e.g. Ram Wrangler "summon a random beast" which can put anything from Captain's Parrot to King Krush on the board). They have acknowledged this problem and generally no longer release cards like that. The only recent exception is Yogg-Saron, which is deliberately designed to be crazy random so it evokes the madness of the old gods. All other recent cards are of the limited randomness type.

Mega-block is also crazy random, and it happens on average every game. Remove it.

I wonder how exactly it makes game so unique?

Also, why did you mention Hearthstone? This is unproductive. Just because problem in a place B (Hearthstone) is bigger than in a place A (PvZH) does not mean that problem in a place A doesn't exist.

Do you realise that there's still huge amount of luck in this game even without instant shield? 

Was your comment directed at me? I discussed Hearthstone because Borisso44 brought it up. No need to convince me. As I explained above I'm pretty much on your side - Megablock should be removed.

I agree. The Insta-Block-Mega Shield, or whatever it's called is infuriating.

I can't count how many games that have been completely changed based on one dumb-luck block.

It's bad enough that it always seems to be a 5+ damage, or game finishing hit that gets blocked. But then they get a card that wipes out all of your creatures, gives all their creatures +3/+3, leaves your hero with one health, kills your dog, cuts the brake lines in your car, forces your wife to miscarry, and then to top it all off, they get to draw a bonus card.

Fun, fun, fun!

I heartily agree with this comment. It is definitely aggravating when you set up a great strategy and just lose due to a block when their meter is empty.

I think the whole counter block with the shield is very cool and I think just having the 1-3 randomness of how much the shield gets filled up is random enough. I think I could accept even having the fill up be 1-4 but the 5% insta block definitely annoys me to no end. And when I'm on the receiving end of the good luck it doesn't feel particularly satisfying either so I don't think it's that much of a win.

My vote goes to removing the 5% instablock and leaving the shield fill up. Perhaps also have other conditions, effects or abilities that fill up the shield more, or recover/remove shields, etc.. It's definitely one of the features that makes PvZ:H unique.