Since pokémon such as regular Diancie, Weezing and Ludicolo are in the compendium, I don't think it will be a bad idea to also add Krookodile. From my experience the only set Krookodile should run in OU is Stealth Rock / Taunt + 3 Attacks with a Life Orb or Dread / Earth Plate. Choice Scarf could be a nice check to pokemon like Mega Aero, Gengar and Mega Manectric, but I think it is pretty underwhelming so I didn't take that set into account.
SSI:
Heatran - It survives any hit from Heatran, Earthquake OHKO's Heatran even if Lava Plume burned but it's only a SSI because Fire Blast does around 75%.
Hoopa-U - The only thing it has to fear from Hoopa-U is Scarfed Drain Punch and the fact that it can only switch in once. If it switches in against a Choice Scarf / Band Hyperspace Fury, Gunk Shot or Psychic STAB, it can trap Hoopa with Pursuit. Against LO and Choice Band sets, Krookodile will outspeed and OHKO with Earthquake.
Toxicroak - It can switch in safely because Drain Punch won't OHKO. It outspeeds and it takes a +1 Sucker Punch really well. SSI in my opinion because after it switched in on Drain Punch, it can't switch in anymore on neither Drain Punch nor Gunk Shot.
Tyranitar - Krookodile only has to fear Defensive Ice Beam, which takes an Earthquake and 2HKO's with Ice Beam or Choice Band Superpower.
Mega Tyranitar - If it switches in on a DD, it will survive Ice Punch and OHKO with Earthquake. If it switches in on an Ice Punch, Krookodile will outspeed and OHKO. It only has to fear DD Superpower.
NSI:
Bisharp - Krookodile gives Bisharp an attack boost because of Defiant, but it doesn't really matter because even a +3 LO Sucker Punch can't OHKO Krookodile.
Excadrill - It is 2HKO'd by LO Earthquake, but it can act as a revengekiller and it also beats Scarf and Bulky sets.
Lucario - Outspeeds and OHKO's with Earthquake. Obviously can't switch in directly but it can come in against a +2 Lucario, survive LO ExtremeSpeed and OHKO in return.
Magnezone - Scarf 2HKO's and Specs OHKO's but Krookodile can revengekill.
Mega Manectric and Raikou - Krookodile survives any hit and OHKO's with Earthquake
Mega Metagross - Not really sure about this one because Hammer Arm still does 85%, but at full HP it can survive any hit even after Stealth Rock damage and OHKO back with Earthquake.
Tyrantrum - Loses to a few things like Superpower, DD Outrage and Scarf Outrage which are all things according to the analysis, but it will always win in a 1v1 situation.