By itself, this card isn’t worth four XP. But if you’re playing a rogue, you make your own luck. Combining this with your teammates covenants means intriguing things, like flipping curses, using them as blessings, and if they end up as curses, taking them out of the bag with false covenant. With sacred covenant, 50% of the time when you draw a curse, which you can trigger intentionally with the pact of the moon, you get +2 and end the check there. Dexter can also use this with a paradoxical covenant, as can Sefina. But with 50-50 odds, you’d better cover both your options, because the accessory slot is valuable and the effect is forced.

A straightforward use for this is as a curse-heavy solo Rogue, at which point this simply turns half your curses into blesses. In theory, this averages the value of all curses to 0.

In practice, of course, you still have increased standard deviation, which is worse than not having the curses there at all... your worst-case scenario still means assuming all your curses come up cursey.

So perhaps the better way to look at it is as an automatic 50% saving-throw-vs-curses. Difficult to say if that's worth a 4xp one-of.