As far as I understand, Necrfomancer is basically a support class. Fragile, with little real self-defense. Ranger is far better, even at lvl.7.
Now, about Necro:
*what statuses (like power etc) are vital to it?
*at low levels - what builds to use to be able to survive?
My disclaimer: I have not leveled a new character for quite some time, can't seem to get myself to do so. Thus, some of my leveling experiences may be *slightly* out of date. Though my most recent attempt to level was a necro.
Necro isn't required to be a support class, just like most classes can do most of the classic MMO roles (support, tank, dmg) relatively effectively. My friend Phenn has done massive amounts of work and theorycrafting about the Necro, and if you are interested, he's got some good posts here. That link actually includes one of the other members of this forum, Dakan's recent~ish experience leveling a Necro. Try out a few different weapons with it, see which ones work out best for you.
As for your question about stats and such, for both the ranger and the necro...it really depends on what kind of build you are going to use, which is generally a focus later on, closer to level 80. I will echo Arkham Creed's comment that Power is a good stat to focus while leveling, it will make killing things faster. A lot of the play with the necro, both dmg and survivability, revolve around effectively using your class skill, Death Shroud.