In an unupped format however, many decks cannot summon a Sanctuary in time to withstand the very denial thats keeping it from play. Thats where Sanctuary falls through IMO; most opening hand Discords or Devourers will beat an opening hand Sanctuary.
Depends who wins the coin toss. Light-elemental with Light mark gets three pillars and a Sanctuary, plays three pillars; Entropy-elemental marshals enough quanta to play Discord next turn; Light elemental plays Sanctuary; Discord is played but fizzles. The only disadvantage Sanctuary has is one extra cost.
The main problem with Sanctuary (like Purify) is that it depends on metagame to fulfill its intended purpose. Sure, Sanctuary is a killer card if you
know you'll be facing someone who uses quantum disruption... that's why the 4HP healing is there: to make its purpose broad enough to be a practical card for matchups where the metagame is an unknown. Most cards have this to some degree - Otyugh is worthless against Immortals, Gravity Shield is worthless against most Fire decks - but when a card's intended niche depends on the metagame as much as Sanctuary's does, some compensation is necessary - and that compensation may become the main drive behind the card's use. I believe we're seeing just that, everywhere but in places where metagaming is possible, like in War and other special events, such as the current Metamorphosis tournament.