'gross is basically outclassed by a lot of things. Offensively, its pointless to run because Steel/Psychic has awful coverage, and while it does have good coverage with the elemental punches, its more useful to use something that can throw its STABs around without getting walled. Its does have access to Bullet Punch, but Scizor outclasses it there, and its has other things that make it a better choice (U-turn). Its Sp Attack is too weak to be scary with a mixed set, and to top it off, it has an awkward Speed tier, leaving it outsped by quite a bit. Defensively, and in the support department, it is completely inferior to Jirachi. Rachi has the same typing, better general bulk, and most importantly, a superior movepool and ability. Jirachi can do everything Metagross can, while paralyzing and flinching things to death, and providing Wish support for its teammates. Metagross can set up SR pretty reliably, but that isn't enough.