I've been wanting to build a team around Shaymin-Sky (fave event mon) since forever, but I need a good core to start with. I know his biggest weaknesses are rocks and frailty, and his most common checks/counters include Ho-Oh, AV Palkia, Heatran, Chansey/Blissey, SpDef Lugia, M-Gengar, Kyogre (dat ice beam), Genesect, and Dialga (big list ;_;). So I'm thinking Defog Rockceus to deal with the most common rocks, Ho-Oh, and Heatran, and then maybe SpDef SubToxic Aegislash w/ Sacred Sword to deal with pink blobs, Lugia, and Kyogre (and bonus of checking non-HP Fire Xern + surprising SpDef Heatran, as well as absorbing incoming Toxics)? And/or maybe DD Mega Tyranitar as the team's set-up sweeper with Pursuit for M-Gengar lacking Focus Blast, Ho-Oh and Lugia again, and Heatran lacking Earth Power.
Shaymin would be able to pull his weight by checking/forcing out Groudon and lesser Ground-types (Hippowdon? Donphan? maybe Excadrill? do they even exist?), who would otherwise threaten all 3 of those options. I'm thinking he could also check/revenge Fighting-types like MMX that would also have a field day with Rockceus and TTar, but I'm not too sure how many other fighting types besides MMX and Mega Luke there are in Ubers.
sorry for the wall of context, but my question is basically:
Is there a better Arceus forme than Rock to synergize with Shaymin-Sky or perhaps something that covers more ground than SubToxic Aegi/M-TTar to round out my core (or on the flipside, someone Shaymin helps out a good deal)?
(as for my Shaymin set and team archetype, it'll probably end up balanced leaning toward semi-stall with ScarfMin carrying AirFlare+Healing Wish as revenge killer/hax0r/last resort support but that could change depending on the core I end up with)