This is way undercosted, but with a higher cost, maybe something like 6 // 4, it might be doable, although that's still quite cheap and it could still be very easily abused with supernova quanta. I'm envisioning some sort of speedbow with 6x supernova 6x SoB, 6x precog dropping the top half of its deck turn 1, while the opponent only gets to draw 1 card from your first shard if they weren't playing first. Another nerf could be to make only one copy playable per turn, or make it unplayable if the opponent can't also get the draw benefit, which will be a huge problem on the first turn.
A few questions on the mechanic:
1) I play this and have a fire mark, I obviously get 3 cards but does my opponent get 2 or 3?
2) I play this and my -opponent- has a fire mark, do they get 2 cards or 3?
Another way of reworking the shard could be something like this:
Cost: 3 // 1 (as zanz currently has it) Each player draws *1* card. If the owner of this card has a fire mark, deal 6 damage to the opponent.
This would help prevent the chaining problem, since less benefit would be gained, while still giving fire a useful bonus, and one that fits the theme of fire much better.
With a 2 card draw, any supernova deck using 6 of these will be really powerful. I'm thinking in particular combo decks like instosis or voodoo universe, and any speedbow are going to have vastly increased win rates. Heck, instosis could probably pull off a sub-5 ttw average with this shard if it only cost 1.