Yeah, Reyla's right. Whoever gave you that advice was a moron. Heck, nowadays, not even MAGES go Conj (and they easily have the most conjuration based spells). Your specialization has nothing to do with your resist rates. As Reyla alluded to, until 63, your dark's lack of a resist mod is what causes your problems more than anything else.
About the best way to help your dots as far as gear goes is with the aforementioned foci. At your first available opportunity, I would recommend ditching the ornate gear for defiant (if necessary). Few reasons for that:
First, ornate gear has the old slot foci assignments. For example, on the Vorshar's set, you have few focus effects (mana pres in the arm slot, spell haste on the feet) and the ones you do have are often minor or only affect one spell (for example, the hands only focus Neurotoxin like the Wizard hands only focus Strike of Solusek).
Secondly, you'll find that upgrading to defiant gives you a ton more mana, better foci, and mod 2s in abundance. It will also allow you to upgrade in the future on a 1 to 1 comparison basis. Right now, if you're looking to upgrade your hands (let's say), you have to trade Neurotoxin focus for COLD damage focus, which isn't really all that important for a Necro. If you upgrade your sleeves, you're trading mana pres for FIRE focus. You see, you have to give up something that might be useful to you for something that may be more situational (though obviously, a fire focus would be more useful on an everyday basis than a cold damage focus).
Thirdly, it's cheap as heck. Keep the ornate legs and robe for their clickies (if you're into that kinda thing) but that gear will make itself woefully inadequate around 65 or so.
If you're on Fennin, shoot a tell to any member of Rendition. I have a freakin' ton of defiant gear stashed on a few mules (I use it mainly for guild tribute fodder, honestly, since it doesn't sell at all).