Ok my thoughts in a nutshell:
Cb Ho-oh to smash and break stuff. Jolly max speed over adamant max Hp to outspeed and pick off stuff like adamant groudon, modest ogre, and neutral natured base 99s. This softens up stuff for scarfed Xern to cleanup with its spammable stab. Synergetic duo bc bird kills stuff that can take xern's mb. This duo is supported defensively by the other mons, with Eleceus functioning as a opportunistic sweeper that can set up on things that otherwise plague the team (read: Palkia with its great 100 base speed and diverse coverage) and either act as a backup win condition or just an offensive powerhouse that forces switches through potent boltbeam coverage and aids the eventual Xern cleanup.
Av palk checks ogre. Av to maximize longevity, important as stab rain boosted water attacks from base 150 spa is incredibly threatening to the rest of the team. Gira checks physical threats in general like groudon, groundceus and ekiller by burning and phazing them. Ev spread ensures +2 LO adamant shadow claw doesn't kill after rocks. Scizor is the obligatory Xern check and second Defog user :o so Ho-oh can switch in as much as possible. Bullet punch is useful priority and is also super effective against Rockceus which is nice because Rockceus is most threatening support arc to this team as it is the only one that can switch in on both Ho-oh's stabs. Eleceus actually is the glue of the team, taking attacks that that team is somewhat weak to if need be, like bolt strike (resisted and will never para) and brave bird (resisted, after which it forces Ho-oh out but only with rocks, more on this)
Weaknesses and suggestions:
NO STEALTH ROCK. Rocks are integral for racking up valuable chip damage, especially important on this team bc it forces many switches which should really be taken advantage of more. For example judgment from eleceus will KO 50% Ho-oh but not 100%.
No status sponge or cleric means status has to be maneuvered around more than the team'd like. Stray toxics really SUCK. Burns suck too. Looking at opposing support arc as status spreaders mainly.
Nothing switches in on psystrike, really. If Scizor gets weakened it cannot function optimally in its role as Xern check.
I recommend using aromatherapy on scarf Xern > hp fire, which is largely superfluous on a scarfed mon (if you predict right you kill that Scizor and lose momentum if you predict wrong you just lose momentum). Also, I recommend a Jirachi over Scizor with the following set
248hp 8def 252spdef calm
Sr, twave, iron head, healing wish/toxic/uturn
This retains your Xern check + deals with MMY + gives you rocks. MMY is still problematic but you can do something like: switch into psystrike --> scout the fire move by switching into Tina - k this point is sorta moot because Scizor can do that too but STEALTH ROCK.
Nitpicks (personal changes): use another Palkia set:
248hp/252spdef/8spd calm
Rest, toxic, twave/fire blast, surf
This gives you a status sponge that retains great longevity against ogre. Scarf thunder does max 29%. Works great with aromatherapy. Also allows you to win 1v1 against many support arceus. Surf still smacks Heatran and Lando. Fire blast smacks Ferro and Scizor. Weakness to opposing Palkia is mitigated bc your team has eleceus and Xerneas. Overall a better team player than your current kia set i feel.
That's all I have for now but I think I got the gist of it down. Nice team, but the lack of rocks is disturbing :o
