Armageddons and Disechants are real problems and I guess the support of Specters and Juzams make that matchup pretty bad
Exalted Darkness' primary weakness is its reliance on two colors of mana
Note that the hexproof only works when it's untapped, but that gives a window to play into
It is a three mana enchantment that if you sacrifice a creature, you return Recurring Nightmare to your hand and put a graveyard creature in play, that is, it is a ridiculously strong card
However, if your off-centered card is a Commander, Modern, Legacy, Vintage staple, or highly collected card, its very likely worth more than its non-off-centered counterpart
Whether you're ramping into a fast The One Ring, casting Grim Monolith, or just dumping out threats, this land gives you raw power without waiting