Teostra. It's not really unheard of. I've made a post a long time ago comparing Staraptor to its true competitor: Talonflame. The differences between the two are noticeable, worth noting, and are the reasonings as to why Staraptor cannot rise easily in
this post.
To bring up to speed, Talonflame's utility, movepool, and ability to use more than two sets are what keeps it high and mighty. It immediately threatens multiple Pokemon, despite its checks being pretty prominent (Rotom-W, Tyranitar, and Heatran being the big three). On top of that, its best set would base itself around either Itemless Acrobatics or Leftovers/Sharp Beak Brave Bird, each with their own pros and cons, but Talonflame does have the ability to set up without relying on Recoil Moves, which ultimately hurts Staraptor; "To Die Young as Late as Possible" is perhaps the best quote to describe it, since its main moves have large recoil amounts. Talonflame can run a utility set up set consisting of Will-O-Wisp/Swords Dance/Roost/Acrobatics or Brave Bird, giving it answers to cripple switch-ins bar Heatran, though you can EASILY fool the opponent with a Choice Band set (as little as it does now) that acts as a semi-fast U-Turn user and Priority sweeper. Staraptor isn't as unpredictable as you make it out to be; Choice Band and Choice Scarf barely have any difference between the two and use, for the most part, the same moves, and will normally be prepared for indirectly. It also REALLY doesn't help having TankChomp and Ferrothorn, the two best Rocky Helmet users of the game, floating around like Politoed in BW, punishing Staraptor even more.
To put this in perspective, let's look at a likely scenario with TankChomp and Staraptor. Both sides will have Stealth Rock up, as is expected.
Staraptor will be left with 75% HP, or 234/311. The opponent switches into TankChomp on a Brave Bird. It DOES deal significant damage, though, 63.3 - 74.8%, but with that said, Staraptor will be taking 1/3 of the stat damage in recoil. Best case would leave it at 146/311, worst case 130/311. Now we have to calculate Rough Skin, which takes 12.5% away. In Staraptor's case, it will be 38, leaving it best case 108/311, worst case 92/311. Finally, Rocky Helmet will be calculated, which takes 16.66% away. This will be 51, leaving it
best case 57/311, worst case 41/311.
Talonflame has a larger Stealth Rock weakness, sure, but it has the ability to Wisp, Taunt (I've seen some variants), or Roost right after since it's not locked into a move.
Looking at stats, Talonflame is actually faster AND has Priority, giving it the ability to spread EVs to other necessary stats like HP (see Bulky Swords Dance). Staraptor is forced to run 252/252 Atk/Spd and almost entirely forced to hold a Choice Item, limiting its usability.
In general, the match-up comparisons show that Talonflame, overall, has a sporting chance more so than Staraptor.
This, though, is just a comparison to its rival. What counts now are two questions:
1. Is it viable in the current state of the metagame?
2. How does it compare to those in the rank above?
In this metagame, Landorus-T, Garchomp, Ferrothorn, Excadrill, Heatran, Rotom-W, Clefable, Mega Scizor, Tyranitar, and the like are HUGE right now. Talonflame has a way around all but three of them thanks to access to Will-O-Wisp, being able to burn every one of the physical attackers listed. Staraptor struggles against Landorus-T due to Earthquake, Garchomp due to Skin+Helmet, Excadrill due to Sand Rush, Rotom-W thanks to Will-O-Wisp and its resistance to Brave Bird, and Mega Scizor due to priority. Its main advantage is that it can hit Ferrothorn, Excadrill, and Tyranitar Super-Effectively with Close Combat, which most people will say holds back Final Gambit's capabilities, but I digress. In comparison to Talonflame, which CAN answer to the common switch-ins, Staraptor cannot, so that is out.
As far as what is in the ranking above, there isn't much in comparison. I'd argue that Entei, as a Physical Attacker, is MUCH harder to switch into thanks to the combination of Sacred Fire (that burn rate) and ExtremeSpeed, making up for forcing Adamant on a Base 100 (event, guys). Sacred Fire's burn chance makes even Landorus-T, Rotom-W, and Tyranitar scared of switching in. Feraligatr is a great Dragon Dance set-up sweeper thanks to Life Orb Sheer Force, letting it outspeed very well after a single boost. Hawlucha is pretty one-dimensional as well, but once Unburden kicks in, good luck. Seismitoad has loads of utility outside of it being Physical. Toxicroak can switch into attacks thanks to Dry Skin. Finally, Mega Tyranitar also has Dragon Dance to boost it well, with deadly STAB combinations and access to Earthquake and Fire Punch (I tried it once...don't judge me). Hell, as a Flying-Type, Mega Pidgeot is scarier to switch into thanks to Hurricane's 30% confusion chance, as well as having Heat Wave and U-Turn for utility.
I love Staraptor, and I love its sheer power it brings to the table, but I don't think it's suited for this metagame at all. It requires too much support to fully utilize, like Tyrantrum (which I also love), is one dimensional like Magneton, and cannot utilize its movepool efficiently outside of "just hit it" like Talonflame can. I'm against a rise, but that's just me.