Agree that this major thyla buff is extremely scary, both in tournaments and in PvP. The extra 500 hp and speed decrease immunity puts it out of range of way too many things. I suppose we will have to see how things pan out.
As for Sarc, it’s absolutely silly. It has an extremely small number of bad matchups, because it has very high damage output, good health, stunning, can’t be slowed, and it can’t get hit by swap in creatures. The easiest nerf it could get is a removal of the speed decrease immunity, so it would fear revenge kills while not experiencing any changes to other matchups (because looking at moveset it’s crystal clear that it isn’t fierce, with no answers to armor or shields). Even the deer, which is supposed to be nearly impossible to outspeed, gets outsped by this crocodile? Seems a bit weird, especially considering neither component has that immunity.
My recommendation is a slight nerf, be it a speed immunity removal so it fears tanks, a small damage nerf so it fears fierce, or the change of resilient strike to fierce strike. All three by themselves make it vulnerable to one of the types of creature, and it wouldn’t change the fact that it’s still extremely powerful.
As for the discussion of buff vs nerf, you have to look at the entire meta to decide the direction to nudge things. It’s lazy and bad design to nerf things out of the meta, and equally poor design to buff things to absurd levels like indo gen 2. If something has a mix of good and bad matchups, it should be in a good place. Sarc has, in its tier and in the unique meta, a shockingly large number of excellent matchups. I care minimally about something being good because it’s a “super hybrid” and care more about the effect it has on its surroundings. It’s not OP, but it’s certainly a candidate for a nerf, the toolkit and stats simply grant it too much flexibility against too many creatures to be ignored. Instead of messing with the stun interactions with fierce, which has horrifying implications (think nitro Thor you can’t stun and quiver in fear), just slightly nerf or tweak sarc so it’s not an issue.