Turin, turin, turin.. once again you have made tons of weird or simply false statements. 
So many if fact that I don't have the time or the energy to correct them.
I've seen this kind of deck before and also tested it. Mark of Death + 6 x Deadly Poison works basically in any kind of deck that doesn't need the extra quantum from mark. Unfortunately it looks better on paper than in reality.
I don't know if you have actually TESTED this deck but I can tell you it pretty much sucks.
Weaknesses:
1. It's SLOOOOOOOOOOOOOOOOOOOOOOOOW......
2. Low winning percentage (you can EASILY lose to level 3 opponent, not to mention a top-50 opponent).
3. The most boring deck ever created by mankind. (no creatures, 2 different non-pillar cards.. click and wait, click and wait, zzz..)
This deck does pretty well against standard anti-God rainbow but is, like I said, SLOW. Death/Water poison deck is MUCH MUCH MUCH faster, works as non-upgraded also and has a better winning percentage.
If someone put a gun to my head and forced me to grind with Fire Bolt deck, I would probably go with mark of water and take 6 x Congeal, which could be used to shut down enemy creatures and give me time to collect that 100 quantum or whatever. Or just take mark of Fire and take Explosions and Rain of Fire.
Scaredgirl you're boring. If you dont like this deck you can tell me, but it works. Having defence isnt a need: i've tested long time a mono-fire with only fahreneits, lances, explosions and a pair of dragons (for non-rainbow opponents), and it worked very well.
Then i havent said nothing about speed compared to poison, and obviously it will take more turns, but you wont have to use abilities and with 18 pillars mana grows faster. I've tried this deck some match and went near to death only against an early lava destryeer PUed after some turn: it was a big problem, and i was thinking about shooting it, but
ai prefer to use sundials if poison is damaging it: that's the point: in most cases you'll have benefits from opponents defences.
About boring: if you think playing the poison grinder is fun you have some problem my dear. I found some fun only in rainbow fast decks, but they're not so effective for farming: too much time.
So about your 3 points:
1. slowness: game time will be not long, having only to look at quanta and pass
2. low winning percentage: try this deck and see
3. boring: not more as every grinding deck
please scared, speak if you've something to say, i like comments and to modify decks with suggestions (obviously this is a dumb deck for grinding and there's few to speak about)
I'll make some more test just to have and idea of winning %. Probably fire/light will be more safer, that's why i called it and hardcore choice: not the best, simply the most unbalanced!
