If fire goes fire stall, I can't see anyway that a single arsenic would change the out come. You would have to get it early for it to do much damage and with the cc in firestall it probably wouldn't last all that many turns. I can't see it being a game changer in that situation. I would expect fractal minor phoenix from fire, considering the event card and the fact they want airborne creatures against us.
No shards has always been the rule I believe and even if it weren't we would have had to have them in our vault.
If we take UG against water, I say definitely keep all six dragons if you change anything because they might have mirror shields and it needs alternate damage. If you want to take anything out maybe trade the shockwaves for a singe OE.
I'll probably be in chat later tonight if anyone wants to discuss decks and strategy.