I try to create removal "tiers". So I'll play bolt as premium removal, but also a lot of the less powerful burn spells.
The danger that burn spells become too good isn't really there imho. They're already all limited by the amount of damage they do. It's only a problem if you cube too many of them, but if you keep the overall number in check you can't do too much harm. Of course that's a different issue than wanting burn spells to cost more.
Agree, six to yourself is too much. Four is already borderline on Darigaaz's Breath, and that one is much cheaper to boot. If anything survives your Inferno, you're probably done for.
It doesn't really help your case for Hour as a finisher if you have to resort to "it's better in other situations". Yeah, obviously it is, but we're talking about Hour as a finisher and a combat trick. If it fails the finisher part that's part of its justification for inclusion gone.
Developing the board: sure you can count turning creatures into 4/4s as developing the board, but that doesn't help if you have to leave mana open instead of playing more of your cards. Being forced to spend mana to protect one of those creatures can happen, not having enough creatures because you need your mana in the end step can happen. That's very clearly another potential downside if we want to use it as a finisher.
You can't just claim 2 for 1s because you upgrade a creature. If turning a creature into a 4/4 flyer for three mana while killing an enemy creature were as easy and profitable as you make it out to be, we'd all still be playing the card. 4/4 flyers are good, but not backbreaking by any means (how many of us have or were close to cutting Serra Angel?). What you said doesn't really address any of the "bad fight card" issues either.
Instant doesn't help you one bit when you topdeck the thing, whereas similar finishers like Overrun can be cast the turn you draw them you have to wait with Hour. Plus if you play it during your opponent's end step you need to have that mana open, so you can't even use the turn you drew Hour to build up your board. It's not necessarily a deal breaker, but it's certainly not ideal.
Also not sure where the 1,5 for 1 is coming from. You spend three mana, a card and exile a creature to create a token that hopefully kills your opponent's creature. In many ways that's worse than a simple fight card, which isn't exactly at the top of the removal/combat trick pile but at least allows you to pick your fights instead of hoping your opponent makes an attack or a block you can exploit while you have three mana open. Even if it works, in the long run your token is more vulnerable than the creature you exiled.
There's a difference between "less effective" and "not working under any circumstance." So I'm not sure why you say Nekrataal is "slightly worse" against black, it just doesn't work against that color. 4 mana 2/1 first strike is not a card.
Only this morning I was listening to the Limited Resources Hour of devastation sunset show, and they heaped praise on the deserts. To the point of them being "if not the best, then among the best few commons in each colour". That already had me thinking that I wanted to re-evaluate cycling lands with you guys. Obviously the formats are different, and HOU has the desertsmatters cards, but still.
If we're reevaluating the card because of HOU, comparisons to HOU matter.
To me the issue is density. Deserts are great because there are a ton of them. You'd have to have several cycles of the Forgotten lands in your cube to replicate that and that's probably not worth it. As a single cycle, 5 cards aren't going to help anyone very much, even in a 360 cube. That'd be a whopping ASFAN of 0,2 Forgotten lands per pack if my math is right. Your chances of seeing even one in a draft aren't great. Nevermind finding one in your colors.
The danger that burn spells become too good isn't really there imho. They're already all limited by the amount of damage they do. It's only a problem if you cube too many of them, but if you keep the overall number in check you can't do too much harm. Of course that's a different issue than wanting burn spells to cost more.
Developing the board: sure you can count turning creatures into 4/4s as developing the board, but that doesn't help if you have to leave mana open instead of playing more of your cards. Being forced to spend mana to protect one of those creatures can happen, not having enough creatures because you need your mana in the end step can happen. That's very clearly another potential downside if we want to use it as a finisher.
You can't just claim 2 for 1s because you upgrade a creature. If turning a creature into a 4/4 flyer for three mana while killing an enemy creature were as easy and profitable as you make it out to be, we'd all still be playing the card. 4/4 flyers are good, but not backbreaking by any means (how many of us have or were close to cutting Serra Angel?). What you said doesn't really address any of the "bad fight card" issues either.
Also not sure where the 1,5 for 1 is coming from. You spend three mana, a card and exile a creature to create a token that hopefully kills your opponent's creature. In many ways that's worse than a simple fight card, which isn't exactly at the top of the removal/combat trick pile but at least allows you to pick your fights instead of hoping your opponent makes an attack or a block you can exploit while you have three mana open. Even if it works, in the long run your token is more vulnerable than the creature you exiled.
If we're reevaluating the card because of HOU, comparisons to HOU matter.