I think Charizards best move set is just his standard kit, 1111. But Im also not a huge fan of customs in general. I think they are cool but they lack a lot of balance and it makes the game feel jank and off kilter. I feel as tho DR doesn't help Charizard (apply to any character and/or custom move) become a better character with better match ups, it just simple gives him an exploitable means of damage that can be hard to get around and needs to be respected or it doesn't change much of anything. Which doesn't lead to fun gameplay for viewers or even the players sometimes, imo.
But that aside, DR is good but I feel like FB is better. DR is great for just trying to catch people and his good on shield but it can be shielded and punished if the opponent has the right character and is fast enough. Its pretty spammable if spaced right but its downfall is that it doesn't lead into any. The positioning it leaves you with its alright but the end lag it has doesn't allow for anything to follow up with other than waiting for their next move. Its a good stand alone move but his move set doesn't compliment it. With FB, all you really need is a good couple reads with a FB and its a lot of damage and or death for the opponent. As long as its not the only move you are using, the damage you take from FB really isn't a bother. Zard is a heavy weight and trading is always in his favour. Reading rolls, other tech chases, follow ups after Nair and covering landings are just some of the ways you can punish people with FB. Its pretty essential to his move set imo. Sure its risky but thats the whole point of the move lol. You can learn how to use it properly and its a very useful tool for him.
As for Rock Hurl, I haven't really experimented with it very much but Im pretty sure it doesn't have Super Armor like Rock Smash does and like you guys said earlier, SA is a necessity for Zard, being so susceptible to so many combos and juggles even. Zards got Utilt, Usmash, Nair and Rock Smash for anti-air options so he doesn't really need anymore imo.