I wholeheartedly agree with pretty much everything you said – I personally don't think torment/hellfire wombo combo is
too strong, I think it's overused throughout extended, which makes the experience rather samey. Consider: 10 of the runes are part of extended, which is chock-full of torment. 9 of them are also chock-full of hellfire. The 5 other runes at least have their respective flavours to them as you collect them: Poison, water, chaos, corrosion (with mutation thrown in because why the hell not), and whatever you want to call Vault's flavour. You could argue that Vaults has no flavour since it has a nonsensical jumble of possible enemies, but I think the Vaults-specific enemies make it unique enough what with recall, mark, and locked doors.
Extended doesn't have this flavour. Extended is just this giant monolithic part of the game which is all about hellfire and torment. I
like Tomb, because it's cohesive design-wise. I wish Tomb were
the "torment branch", with torment starring in Tartarus as well but to a lesser extent. However, all of Pandaemonium and Hell feel really samey. It shouldn't feel the same way to play through Gehenna and Dis, but it really, really does. They're both just full of torment and hellfire, with bosses that throw hellfire at you.
It's a design challenge how to improve upon these issues, but I definitely think it's a desirable goal for the devs.