Engineer or Necro
Keep playing them both to 80, at level 15 your still getting a feel for the classes. After playing them both for a longer period, fully unlocking utility and elite skills you will probably be able to make a solid decision on which profession you prefer to play.
I found that for most classes I started getting the hang of them at level 40.
Your description of the classes are right, enigneer has more versatility you can do control, support and still do decent damage. Necro is hard to kill but I have not yet played one.
My top two are Ranger and necro with warrior at three ( very versatile with weapons ).
Agree you should get to elite skills to get the feel.
I would go with Engi cos you rarely see them and I’d like to see some variety =P
Atm I think that nocros are kinda cool
I like to run around with a staff after using swords, bows and pistols on my other champions ^^