I think the problem with Oath is its very matchup dependent. If you get a turn 2 Oath against White Weenie, that's pretty much the game; it's not like they can afford to not play creatures. But Oath against a Superfriends control deck is a dead card. As for where to slot Oath into, RGx Sneak Attack is very strong. Sneak Attack, Channel, Oath, and a handful of Eldrazi wins games.
[180 classic cube]