Ah, that's too bad Arcvasti, it always seems to go that way when you get an early bonus like that potion of XP. You say your defenses were bad, how much dodging and fighting had you trained? Also, komodo dragons aren't faster than you, running away might have been an option. At least you could probably have dragged one up to another floor, so you only had 1 to deal with at a time. Komodo dragons are no joke, those bastards hit hard.
I also wouldn't typically wear plate on a MF, unless it had a really good enchantment. The rule of thumb of EV+AC would probably have shown that you had better defenses in something like ring mail. The MF I just played was very atypical, but when Oka gives you a +9 CPA, you wear it...
Player ghosts have infinite MP, flying, and undead immunities, so they are tougher than the actual character. Their weak point is there's no longer a human controlling them, so they're stupid. With tough ghosts I'll usually try to fight them while standing on a staircase, if it seems possible to win I'll keep trying that, going up the stairs when the fight isn't going well, then trying again. If it doesn't seem winnable, or the ghost has a weapon of draining or something, I'll just try to bypass the level, or just explore normally and run to the stairs whenever the ghost shows up. Annoying, but effective.
Necromancers are a challenging class in a way. They have pretty powerful spells, but as you said, they flat out don't work on some targets. So yes, a necromancer generally has to hybridize much earlier than most (But remember, it's really easy to just walk away from most zombies, skeletons, and imps).
My most enjoyable necromancer games have been with kobolds. I'll pick up the first short blade I see, and train that a bit. At the same time, I'll train a bit of necromancy, and dodging (I train dodging on almost every character I play from start to finish. There is almost no time you shouldn't be training dodging).
The general strategy is typically to use pain and raise skeleton early on to manage through the first couple d levels, at which point you should find a short blade. Even before you find a short blade, pick up the first weapon you see and wield it, it's better than your bare hands. Once you do find a short blade, it's a good idea to train it a little bit, but don't be in a rush to hit min-delay. It's a backup weapon, against enemies who are dangerous to you, you should run away, not try to dagger them.
After you clear a few d levels, your highest skill should be dodging, thanks to kobold's nice apt for it. Also enjoy eating all the meat, for some reason intrinsic gourmand makes me so happy...
You'll find that even with relatively low AC, high EV makes you quite survivable. You're not a squishy mage, you're an agile hybrid.
For god choice, you have a number of options. The obvious one is Kiku, but I've never particularly enjoyed that god. Still, it's a good choice. Other good options are Ru, ash, makhleb, dith. Oka isn't a bad choice if you want to lean more toward fighting over magic, or if you just want be able to shore up your weak skills when you do have to get into combat. Trog is a very effective choice, because he's trog, but I assume if you're playing a necromancer you actually want to play a necromancer, not a berserker with a book to burn.
I'll generally just keep following this strategy, probably training some fighting here and there early on, and then just leaving it on after I have short blades in a good place. I'll start training some conjurations after I have bolt of draining memorized to get its success up, that's a really good spell. Bolt of draining will take care of most of lair pretty well. If I find a buckler I'll switch dodging off temporarily and train shields until I have most of the penalty eliminated (You need 9 skill as a small race to eliminate buckler penalties, it's not worth using a regular shield s a kobold) At some point, I'll train some stealth to get better distraction stabs, maybe even kill a sleeping enemy once in a while. Obviously if you went with Dith stealth becomes more valuable to you, but don't fall into the trap of depending entirely on stabbing. Dith on a necro is only partially for the stealth bonus, the shadow bolts are the other big reason.
Everything after this point really depends on what happens to show up for loot, and what your god does for you. If you find a book with mephitic cloud, it may be worthwhile to spend a little extra XP on conjurations and spellcasting to get it going for some good stabbing opportunities.
Eventually, the way I play this combo, I try to either get a pain weapon, or excruciating wounds. Pain is a fantastic weapon ego for someone with high necromancy skill, as it just adds up to your necromancy skill in damage to each attack. If you can get your hands on a quick blade with pain, you'll really appreciate its power, but even a dagger with pain is great. I'll typically have spent a reasonable amount of XP on conjurations, so a few non-necromancy damage spells are a good option for negative energy resistant enemies.
So... what should I play next? I have an opportunity for a streak, but the recent discussion has me thinking about playing either a KoNe, another MfGl who will hopefully be a little more typical for demonstration purposes, or maybe a Troll aiming for statue form.