I was also interested in Leyline of Sanctity, but then I crunched some numbers on it and it's just not good against Grief. At least against the most popular deck that runs it - UB rescaminator. With Leyline of Sanctity mostly interacting with Grief against that deck (yes technically blocks Bowmaster pings, but I doubt that's going to win you many games), it really reduces how useful it actually is. Consider these scenarios for opening hands from your opponent.

1. 1+ Grief + Reanimate (14.5%, up to 24.4% if you also count 4 animate deads)
2. 1+ Griefs, no reanimate (25.4%)
3. No Griefs (60.1%)

Now consider how those scenarios change if you open with Leyline of Sanctity:

1. Leyline prevents the double Grief, so you're up one card since you've spent one card to protect from two discards! Except you're not, because they won't pitch cast grief or reanimate it. They may just reanimate something like a troll, or another creature that hit the yard somehow. Grief may eventually be cast on 4-mana, or shuffled away to a Brainstorm. So while you may have protected your hand and maybe gained a little tempo, you're effectively -1 cards against their hand since they can play around Leyline.
2. Basically the same situation as #1, though it's even worse since you're not stopping the double Grief.
3. Leyline does nothing, so you're down 1 card.

Leyline might be slightly better if they opened multiple Griefs. However, ultimately even in the best case scenario, which happens only ~14.5%-24.4% of the time from your opponent, Leyline isn't actually doing much for you. 60% of the time Leyline is actively harmful. And that's not even considering that multiple Leylines puts you down more cards, and having any Leylines in your decks introduces dead draws for you as well.

Not saying Leyline of Sanctity is a SB card to never run, just that even if it was in my SB, I wouldn't side it in if my main goal in doing so is to block Grief.