I was learning German at school when I first read Dune and "pronounced" Sardauker as if it was German. Some years later a friend and I had an argument about how the names were pronounced and he particularly objected that.
Personally, I think it's Ben-ay (rhymes with day) Jes-er-rit.
Dune has a few ambiguous or difficult pronunciations. I don't think there's a way to pronounce "Tleilaxu" that sounds cool.
I thought T'lie-lax-oo was OK.