Update on my thoughts:

MD: the generalists
3x JGCA
1x Sphinx
1x Archon
1x Iona
1x Hexproof/Shroud slot (Inkwell seems to be the best ATM)
(1x Flex slot - Elesh Norn or a 2nd copy of another creature. Often Sphinx.)

SB: the specialists
1x Terastodon
1x Elesh Norn
1x P.Emperion / META slot
(1x META slot or 2nd copy of MD creature. Often Iona / Sphinx.)