I voted against the return of Latias to OU, not because I truly believed Latias was broken, but because I was against the entire idea of the suspect test. I believe Jirachi is the much more clearly unhealthy Pokemon, and should have been addressed first (The results of the recent suspect test don't really tell us if Latias would be OP without Jirachi as one of its main checks around).
I believe that Jirachi is an incredibly unhealthy Pokemon due to both its incredible versatility aided by its great typing, its overall effectiveness, its lack of counters, and the luck it introduces into games.
First, it's versatility. Jirachi has one of the most diverse movepools in the game, and the impressive stats to utilize them effectively. Nothing can run a wider variety of sets than Jirachi can. It can function as team support with Stealth Rock and Wish, a utility check, a revenge killer, a physical sweeper, a physical sponge, a special sweeper, a special sponge, a mixed attacker/stallbreaker, and a crippler. It stats are good enough that it can often perform several of roles simultaneously. It can easily fit into every single team archetype with its versatility. Its physical movepool including Iron Head, Thunder Punch, Ice Punch, Fire Punch and Body Slam harms almost everything. It's special movepool including Psychic, Thunderbolt, and Grass Knot can hurt many mons that check its Physical stab.
When you first see a Jirachi, the only real tell you have as to what set its running is the presence/abscence of Leftovers, and that still leaves many options either way. Nothing switches into a Jirachi completely safely, because many of its presume counters can still at least be Statused/Tricked.
What consistently counters a mixed Jirachi? As a first requirement, high physical bulk or steel resist are necessary, otherwise Iron Head flinches are too big of a risk. I would argue that only pokemon with Rest can truly be considered counters, with Natural Cure users (Starmie and Celebi) coming in a distant second. Heatran and bulky Rotom (sans rest) nearly counter mixed Jirachi, but can still be crippled by status. Bulky waters are still threatened by Thunderbolt/Grass knot + Paralysis. Bulky grounds are threatened by Grass Knot + Paralysis, bulky steels (sans Heatran) are threatened by Fire Punch or Thunderbolt (Empoleon/Skarmory)+ Paralysis. Also, every Jirachi switch in besides Fire types are risking a burn when coming in on Fire Punch.
Steel typing + Serene Grace is what makes this Pokemon truly evil. The steel typing is essential for giving it STAB on its 60% flinch rate Iron Head, as well as allowing it immunity to sandstorm (i.e healing with Leftovers). The constant healing allows Jirachi to survive for so long, combined with the 20% odds of many good checks being severely compromised by Fire Punch burns can make it feel like over time odds always favor Jirachi. Leftovers healing over all the turns spent being flinched by Jirachi, along with very good (100/100/100) defenses make this Pokemon extremely durable, which is problematic because over time it will muscle through everything except for Heatran and Bulky Rotom.
Closing statement, every DPP veteran has seen and experienced games where Jirachi users get obscenely lucky and win in situations where they should have no business winning. Can it really be argued that the hax it introduces into games is healthy or competitive? I will sift through my replays for evidence if people think its necessary or desired.
I believe that Jirachi is an incredibly unhealthy Pokemon due to both its incredible versatility aided by its great typing, its overall effectiveness, its lack of counters, and the luck it introduces into games.
First, it's versatility. Jirachi has one of the most diverse movepools in the game, and the impressive stats to utilize them effectively. Nothing can run a wider variety of sets than Jirachi can. It can function as team support with Stealth Rock and Wish, a utility check, a revenge killer, a physical sweeper, a physical sponge, a special sweeper, a special sponge, a mixed attacker/stallbreaker, and a crippler. It stats are good enough that it can often perform several of roles simultaneously. It can easily fit into every single team archetype with its versatility. Its physical movepool including Iron Head, Thunder Punch, Ice Punch, Fire Punch and Body Slam harms almost everything. It's special movepool including Psychic, Thunderbolt, and Grass Knot can hurt many mons that check its Physical stab.
When you first see a Jirachi, the only real tell you have as to what set its running is the presence/abscence of Leftovers, and that still leaves many options either way. Nothing switches into a Jirachi completely safely, because many of its presume counters can still at least be Statused/Tricked.
What consistently counters a mixed Jirachi? As a first requirement, high physical bulk or steel resist are necessary, otherwise Iron Head flinches are too big of a risk. I would argue that only pokemon with Rest can truly be considered counters, with Natural Cure users (Starmie and Celebi) coming in a distant second. Heatran and bulky Rotom (sans rest) nearly counter mixed Jirachi, but can still be crippled by status. Bulky waters are still threatened by Thunderbolt/Grass knot + Paralysis. Bulky grounds are threatened by Grass Knot + Paralysis, bulky steels (sans Heatran) are threatened by Fire Punch or Thunderbolt (Empoleon/Skarmory)+ Paralysis. Also, every Jirachi switch in besides Fire types are risking a burn when coming in on Fire Punch.
Steel typing + Serene Grace is what makes this Pokemon truly evil. The steel typing is essential for giving it STAB on its 60% flinch rate Iron Head, as well as allowing it immunity to sandstorm (i.e healing with Leftovers). The constant healing allows Jirachi to survive for so long, combined with the 20% odds of many good checks being severely compromised by Fire Punch burns can make it feel like over time odds always favor Jirachi. Leftovers healing over all the turns spent being flinched by Jirachi, along with very good (100/100/100) defenses make this Pokemon extremely durable, which is problematic because over time it will muscle through everything except for Heatran and Bulky Rotom.
Closing statement, every DPP veteran has seen and experienced games where Jirachi users get obscenely lucky and win in situations where they should have no business winning. Can it really be argued that the hax it introduces into games is healthy or competitive? I will sift through my replays for evidence if people think its necessary or desired.