Let's talk about Slayers and Reavers (the Rituals). Feedback from playtests so far has shown that they have real balance issues in their current form, especially against Undead, and I strongly suspect that they are going to be changed significantly after the Playtests are complete.
We have lots of other things to Playtest and see how they work, especially versus Undead.
Because of this, we are encouraging players to consider other Rituals and *not* to take Slayers / Reavers (especially Undead Slayer) - both (a) to help validate how other Undead changes balance without Slayer in the picture skewing the results, and (b) to make sure that players get a chance to playtest their own builds and Magic Item options without having a potentially skewed perspective by using Undead Slayer to solve all problems. We are not prohibiting players from bringing these Rituals - you can if you really want to! - but it may affect your playtesting experience and may throw off your expectations for "final" 2.0.
Separately, keep in mind that the location you are heading to in-game is one that has "used" the 2.0 rules for a long, long time (this was noted in the in-game hooks that were released), and that in-game creatures there may have looked at in-game "protections" from Slayers and Reavers.
-Bryan