If only I had the ability to speak about some nice Necro builds, unfortunately for me, no beta invite yet
That said, Ive seen some videos and the Necro seems to be a very powerful class, but they'll probably tweak all the abilities/sets and stuff.
Ive seen lots of necro's just fresh lvl 70 doing T8+ solo easily.
EDIT: And with that i'm trying to say, i don't really think there are any 'builds' out yet.
Just like the intention of the beta, we're just gonna have to test the skills and see what we'll get next update.