Before we delve into how to perfect a pokemon, we need to look at if its role is really necessary. Yes the listed pokemon take miniscule damage from Espeed and can all survive at least one HJK, but the issue is that they fail to do anything else and that they will have issues killing a Slaking indirectly. Not to mention that Jirachi can do better things with Shell Smash Stored Power.
If you want to be able to reliably take on Slaking something interesting to look into is Terrakion. Someone brought him up a long time ago on PS and I looked into him, and was pleased with the results.
Terrakion @ Lum Berry
Ability: Pure Power
Nature: +Spe, -SpAtk (Jolly)
252 all
-Extreme Speed
-Close Combat/Hi Jump Kick
-U-turn/filler
-Shadow Force
The big selling point of Terrakion is its two-fold ability to survive an Extreme Speed from Slaking and ohko back with Close Combat. What's even more interesting is that if your opponent steals your Slaking with Blissey netting him a Slaking with a monstrous 255 base hp, Close Combat will still kill guaranteed providing Rocks/Hi Jump Kick alone. Shadow Force scares Slaking out prompting a switch in to Slaking, who is then dispatched with Close Combat/Hi Jump Kick. I haven't figured out a specific use of the filler space yet so I'm sticking with U-Turn.