You really don't want to see my arena deck right now :p It's 30-0 with lava golem as the card. *hangs head in both shame and pride simultaneously* I've built a couple monofire or almost monofire decks in the past if I get a good fire card, but I don't try to make every deck into an almost monofire just because it'll work. There's people that will, for instance, get a card like Shockwave and make a monofire deck and cast it off the one air from Cremations. I don't like when people do something like that, because it's not particularly imaginative, but like I got handed lava golem two days ago... I'm not going to pass that up unless I already have a good deck up, and my deck was 7 days old when I got golem, so of course I was going to use it.
Personally, I don't see fire stall as being as much of a problem as immorush, but maybe it's because immorush does better against my style of decks (usually slower rainbow control types) than fire stall does. Also, most of the cards that I think are the biggest culprits are used more in immorush than firestall.
Two of the worst offending cards in my opinion:
Explosion - This is just too cheap. It's so cheap, you can splash it in other decks by just making your mark fire in an otherwise mono deck. When compared to other permanent destruction (Steal, Pulverizer, Butterfly Effect, lucky mutants) I think it should cost at least 1 fire more in both forms. (Granted, this is also used in firestall)
Cremation - This is really powerful. In fact, most of the games I beat immorush, it's because their draw had few or no cremations. It could be changed to only work on fire creatures, or give less quanta on nonfire creatures, or require 1 fire to actually play it, so that it either takes 1 extra turn to play it in pillarless decks, or you have to use something else (nova, upped tower) to power it out on turn 1. Many times, with just one more turn, I'd be able to stabilize against such decks, or outrush them if that was my strategy.
Also, fire has the creatures with the highest offense/lowest defense ratio. This means that, in the absence of creature removal, fire is the best element. However, this also is one of its weaknesses, and can be taken advantage of by cards like otyugh, antimatter, and so on. I think that crimson dragon is reasonable, though strong, for instance, but I do think that minor phoenix and lava destroyer are too cheap. Minor phoenix should either cost 1 more fire to play, or be 3/1 at the current cost. Lava Destroyer is just... scary :p It should cost at least 1 more fire to play as well; it certainly should cost more than the unupped version, which is still a strong card, but more fair.
Well, that's my two cents. At least my lava destroyer arena deck is slightly unique, or at least as unique as can be done with such a card. It's got the core of the deck we all know and hate (6x destroyer, 6x gemfinder, 6x cremation, some explosions) but it's got a few cards on the side that aren't usually in such decks. Even if I'm going to follow an established archetype, which I try not to do, I will stamp my own style on it because I don't like netdecking; it shows a lack of skill, and often, they aren't optimized anyway.