252SpAtk Jirachi (Neutral) Flash Cannon vs 0HP/0SpDef Reuniclus (Neutral): 34% - 40% (126 - 148 HP). Guaranteed 3HKO.
252SpAtk Jirachi (Neutral) Flash Cannon vs 0HP/0SpDef Gothitelle (Neutral): 36% - 42% (102 - 120 HP). Guaranteed 3HKO.
252Atk Jirachi (Neutral) Iron Head vs 0HP/0Def Gothitelle (Neutral): 40% - 48% (114 - 135 HP). Guaranteed 3HKO.
Reuniclus does have slightly lower defence, but a marginally better Spdef. On the whole Reuniclus is slightly more bulky. Also it probably should be mentioned that Duosion hits just as hard as Reuniclus. Despite sucky coverage I think Reuniclus can make Middle [3/3].
Absol for Middle [1/3]. STAB Sucker Punch of that Atk is awesome, but that speed and those defences really hold it back.
Grumpig for Lower-Middle [1/3]. Basically it's Gothitelle with worse defence and no Thunderbolt, but has better speed and no babying.
Mamoswine for Lower-Middle [2/3]. Found far too late in the game and doesn't really make it up in the remaining battles. It's a shame Swinub isn't available somewhere as you're stuck with Ice Fang otherwise.