Sure, but if you're the one spending 4+x mana for symmetrical damage that seems like it could open the window for other decks to take advantage. Even if they're normally less aggressive, they've got a huge mana advantage on you.
Adding black is definitely a big add, but personally I'm just not that into a trade of making my commander much worse in order to add a color. It might work out okay in the final analysis but it seems a lot less fun to me.I think you're undervaluing having access to black in a torbran deck. Demonic tutor is a helluva card and having flying and haste and creature removal on torbran is nice. It's not just "adding a color" it's adding one of the best colors and adding some utility
I think it's more different than worse than torbran; the ability to remove blockers is real decent.
I suspect R&T are probably a lot more creature-based than Torbran Solo, given that combat damage is probably the easiest way to take advantage of the damage in an asymmetrical way, so maybe they do have creatures to burn? It seems a lot less focused though.