Hey Chris
The snorkel itself still allows cool air to be 'rammed' into the engine and hence is still a benefit, but yes, a bit pointless without the breathers. The diffs, transfer and gearbox all need the breathers extended to avoid water damage if doing crossings. That damage is expensive generally, so the breathers are more than worth it - if you're doing it yourself, you'd pick up a kit for around $100, or be looking a close to double that to have someone do them for you. The front diff may already be up in the wheel arch, and the rear above the rear crossmember, so it's only an extension of the rear and installation of the other two!
Good luck.