It's not the total mana value of the two cards.
In 2009, Flygon Lv.X was one of the strongest cards around, but in the 2010 season, Garchomp C (C) is able to quickly counter Flygon with its Colorless Weakness
Heliod, God of the Sun Heliod, God of the Sun does a great job enabling an aggressive, go-wide strategy by letting you attack without worrying about the consequences of a crackback and providing you with an undercosted, indestructible attacker
Faith of the Devoted: As much as I have frowned on Cycling, this enchantment makes me want to put all those Cycling cards in one deck and four of these
Hydreigon ex, which makes an appearance with its Tera crown, looks terrifying and immaculate in equal measure