I quite like the shield in that deck. Apart from anything else, it isn't defending, it's creature control, which is kind of fire's secondary strength.
I've come across it a few times in top 50 and fire wall is beast against, to name a few usually game-breaking cards, ffq, bone/graveyard, otyughs (can never get above 5 health max, making them easy prey for a couple of rains of fires).
Raw power, I thought about swapping 2 of the crimson drags for lava golems in my version but there's just no point - you merely spend precious grinding seconds clicking 'Growth' each turn
Does it work without brimstone eater tho? cos if it doesn't, it's gonna be hard for people to grind just to GET the grinding deck. Can they be replaced by pillars with minimal effect?
EDIT: Oops you answered that in your first sentence. Sorry >.<