If you have to reset so much to catch something, that raises the question if it's worth the time and the annoyance in an efficient run. That doesn't apply just to the legendary birds, but Snorlax as well.
I used Snorlax in my recent run and was very dissatisfied with the results. For one, he's slower than pretty much anything, which is a big con in-game. Not only do battles take longer to finish, but sleep, paralysis, accuracy falls, critical hits, flinching - all of that may prevent Snorlax from getting his quick kills, and when you think about it, there are only so many enemies that Snorlax can fight without being afraid of the aforementioned annoyances. Sure, with that bulk, he'll never die unless you send him out against a fighter, but I'd prefer to just sweep through things quickly.
I'd still say that Snorlax is the best Pokemon for Sabrina's gym, assuming you teach it Shadow Ball (which is a substantial investment).
I'd also argue that Pikachu needs to reside in the Top tier. Good attack, special attack and speed, takes on earlygame Pidgeys and Spearows very well, plus for non-Bulbasaur starter teams, Pikachu is pretty much the only hope against Misty's Starmie who's very tricky to take on at that point (unless you miss the gym and come back later, which is very uncool to do).
Sandshrew needs TMs in order to be good, and while you can have as many Dig TMs as you want, he suffers in usefulness because Earthquake is so far away, and his attacking options are very limited.
In general, I think Psychic-types reign supreme in FR/LG, and Ground-types are less useful than in RBY. Levitate Koffings/Weezings are all over the place (most Rockets and Bikers have them on their teams), not to mention Gastlies.
I think for that reason alone Abra and Mr. Mime should go to Top Tier, and Jynx should be at least in Mid.