The Jank Queen
The odds of beating a mon you 3HKO that 2HKOs you is 84% (assuming no crits happen), you simply calc the chance that neither flinches (=the chance you lose) 0.4x0.4=0.16 then subtract that from one 1-0.16=0.84 which is a point both the pro-ban and anti-ban seem to be forgetting.I have to interject here and add something. This sixty four percent chance that you state is only applicable if you are facing off against a foe who is able to OHKO you. This is a different story with a pokemon who is unable to OHKO you.
If said pokemon facing off against Jirachi can only 2HKO at best, the odds get noticeably better for Jirachi as it can afford to miss a flinch as long as two other attacks manage to flinch.
Let's break it down Jirachi's 3HKO against a somewhat tanky mon that can only 2HKO it.
0.6 (flinch) x 1.4 (no flinch) x 0.6 (flinch) = 0.504
0.504 = 50.4%
(EDIT: Didn't realize in my drowsy stupor that the example I used is for a 4HKO instead of 3 hits because the second flinch needs to matter. This only strengthens the argument though because these odds mean that Jirachi can coin flip wins and losses against a mon that it can only 4HKO, even if the opponent can 2HKO Jirachi back.)
As you can see, an inability to OHKO jirachi while still getting
3HKO'd4HKO'd by Jirachi raises the odds a great deal in favour of Jirachi. That 64% chance of losing has now dropped to only 49.6%; basically a coin flip.
The point that I am trying to make is this: Most times in 1v1 whenever there is a very close matchup it boils down to EV investments and skill at mentally outplaying your opponent (and vice versa). Jirachi turns this logic on its head and creates "close" matchups purely through luck.
Also, I have seen the argument that basically says "Relying on luck isn't a very good competitive strategy, so it isn't broken because it doesn't get consistent results." Will you feel this way when you are on the receiving end of such a strategy and losing? Will you feel this way if you see someone who just happened to get lucky and be okay with it simply because you know that the odds dictate that they have to lose at some point?
It's already late and I am struggling to keep my thoughts aligned. I will talk more about this another time.
These matchups are incredibly rigged in Jirachi's favor