Let's see. Cofagrigus has great defenses and can spinblock pokemon but Jirachi has wish support and Paraflinch. It depends on which suits your team most. I'd Suggest movesets like:
Cofagrigus @ Leftovers
Evs: 252 Hp / 136 Def / 120 Sp.Def
Nature: Bold (+Def, -Atk)
- Shadow Ball or Hex
Rest is his only way of healing. Haze is simply just a filler. Shadow ball does a nice amount of damage while hex does a little bit more while the burn damages over time. Will-o-wisp is just Will-o-wisp.
Jirachi @ Leftovers
Evs: 252 Hp / 224 Sp.Def / 32 Spe
Nature:Careful (+Sp.Def, -Sp.Atk)
- Body Slam or Thunder Wave
- Iron Head
- Fire Punch or protect
Body Slam or Thunder Wave to cause Paralysis but Body Slam can't hit ghosts while Thunder Wave can't hit Ground. Your Choice. Iron Head is flinch. Wish for healing and passing it to others. Fire Punch to get by those Steel types(I'm looking at you Scizor and Ferrothorn). While protect is protecting for wish and/or leftovers.
Choose either one for what suits your team!