I am running a Pharo3.0 image (with an older Voyage) against MongoDB 3.2. I think I am already using "WiredTiger" as database. If you can reproduce it, we can have a look. The only issue I have seen is Sabines authentication failure with more "modern" schemes.

I have Pharo 6 and the newest Voyage + MongoDB 3.4. I successfully connected and was able to add new collections. The only problem was that I couldn't access existing collections created in MongoDB.��

I don't have access to my computer at the moment, but I will try your first suggestion and let you know how it goes.