In PTR, some of unique stats even lower then normal. It at least 1.5 times than normal. But I do not agree with the idea that it should tempering once. It will be better for them to have much more powerful uniqur stats to make them unique.
I am sure they will change the uniques to fit the new itemization. Anyway, you can level up them up to 12 and every 4 levels you get a random overpower in one of the afixes.
I’d actually like if you could imprint uniques abilities onto other legendaries because it’s annoying to lose a power or have to swap it out for another power that you lose.