They LOOK way too similar IMO, but they sound completely different. I wouldn't use them together, mainly because I can see Jens being prn. wrong. Although, I'm starting to love the name Jude!
I agree.They would be okay if you never had to write them down next to each other. And I think that Jens would be really likely to be mispronounced, especially paired with Jude, which would make people more likely to assume Jens is pronounced with a J sound.