Hello there. I've noticed some spots in my cube (and I'm sure many other cubers) seem overcrowded. My biggest glut is 4 drops in red. I have 10 of them in a 360 unpowered cube. I'd love to get down to 8, but I'll settle for 9 (or even staying at 10). The main 2 things I want to discuss are:
1. How do you rank the 4 drops in red? What is your criteria? What should I consider cutting (or even adding)? Here's the 10 I'm running. Feel free to add more to the mix:
Sneak Attack, Chandra, and Fiery Confluence seem uncuttable from a power level perspective. Purphoros is powerful and helps define a token strategy and is splashable. Pia and Kiran Nalaar is great in non-aggro red decks (and I do support artifact synergies), but harder to splash. Flametongue Kavu is good, splashable value. The rest of the cards shine in aggro strategies so I should find one to cut, but they're all so potent. If I had to define a group of cuttable options, I'd go with Pia and Kiran Nalaar since red doesn't have a ton of synergy with artifacts, Flametongue Kavu for being a bit boring, and whatever the weakest aggro card is.
2. In your cube, how heavily to you factor in curve when compared to power level? This is a general question so feel free to take it where you want.
With both Hellrider and Koth, I think you can easily skip Hero of Oxid Ridge at 360, and maybe even Hazoret too. The others I'd keep for sure. Purphoros isn't a must unless you really support a good token strategy for players to bbuild around. Daretti, Scrap Savant is a 4cc card I love in red, but it's expendable if you're not supporting the artifact.dec. Even without artifacts, I think Pia and Kiran is still a great card, and while boring, FTK is still a solid dude. The splashable cost is helpful for a lot of manabases.
I think your weakest and cuttable cards are Hazoret, Pia and Kiran Nalaar, and Purphoros. A lot of people suggest removing Hero of Oxid Ridge if you already play Hellrider, but to me Hellrider is by some distance the best aggressive red 4-drop, and Hero does an extremely decent Hellrider impression.
I am playing everything you have listed, except Hero, and I include Daretti, Teritorial Hellkite and Rekindling Phoenix. That is at 720, so you are definitely over the top. Of everything you wrote, I'd definitely cut Hero, he is reliant on board presence and is weak to blockers. I also think Hazoret is cuttable due to consistency issues and overcrowding of the aggro-only 4 drops.
I like Pia and Kiran as a multiple role card. Good in token decks, artifact decks and more minor interactions with blink and 2-power matters (like Alesha). Still a great card at face value for slower red decks, as it provides three blockers, 2 of them in the air, and pressures planeswalkers very well. I prefer them over FTK unless your cube is excluding a lot of the synergies and the demand for non-aggro red 4 drops is very low. I'd also play them before Purphoros, as it's sub-optimal to play a token payoff card without playing the good, generally playable token producers first.
I'm at 400 and play Chandra, Torch of Defiance, Koth of the Hammer, Hellrider, Hazoret, FTK, Pia and Kiran, Fiery Confluence, Purphoros, Sneak Attack, and Experimental Frenzy. I almost don't even count Sneak Attack and Purphoros in the conversation with the others, since they're archetype support. So is Pia and Kiran, to an extent. I used to play Daretti but cut it because the artifact deck got to be a little too on-rails for my tastes. I could cut Hazoret and not be too worse for the wear, but it's a fun card. Frenzy is new and I like to test out newer cards for a while, especially when they kick my teeth in in other formats.
I'm not sure what I would keep at 360, but I think I'd play everything on IMorphling's list except Splinter Twin. I'd try to cram Purphoros in there too, just because he's a fun build-around. If I was still supporting the artifact deck, I might swap out Koth for Daretti, but I doubt I'd have room for the deck at 360.
Not much to say in regards to the op, but honestly after the first 3 cards you could probably get away with not playing any more red 4s if you wanted, they're good but certainly not remotely as good as the first ones and don't typically warrant splashes.