Neither of those pokemon wants to switch into TR Hera. Clefable gets 2HKO'd Bullet Seed, and Azu goes down hard to Bullet Seed.Disagree. M-Heracross has around that speed iirc, yet it is among the only viable tr sweepers we have left. Clef is one of the go-to switch ins for M-Heracross, but that hasn't affected the usage of herra too much. Azu wrecks tr herra 1v1, smashing it with Play Rough, bit despite this, tr M-Heracross is still a viable set. Victini is another great example of this, being a lot faster at base 100, except Victini has a powerful move to lower it's speed, so being under-sped isn't as much of a problem. I'd say higher than base 100 is too fast for tr, but anything lower is absolutely fine, with some team support.
Don't get me wrong though, Tyrantrum is still a piece of crap.
But I agree with you about the speed thing. I think 80 is the cap, unless you decrease your speed like Victini. Honestly, speed isn't that big of a deal with so many fast top tier pokemon running around in ORAS. No one is going to nerf their speed just for TR, when it means being outsped by paralyzed base 100+s.