
Kolokotroni |

Yes, I've used one as an npc, and I've also had a player play one briefly.
My experience is its an interesting take on the classic necromancer. Using modified leadership rules for an undead hoard instead of controlling them via create undead made for an interesting encounter. I find that and it's companion the death knight to be interesting to play from both the mechanical and a flavor perspective.
My player enjoyed it well enough in the one shot he used it in, but decided he liked the flexibility of wizards better then the specialization present in the death mage.

Writer |

I simply prefer using a Juju Oracle. I can duplicate the Death Mage with one feat: Undead Leadership. Granted it's from 3.5, but as the only GM's i know that are cool with me playing a necromancer are GM's who've had enough experiance to fondly remember 3.5 I can usually get it (though I prefer regular Leadership so i can command both living and dead ^_^)

Question |
Hmm...yea the issue from what i see is that the death mage is easily replicated by other classes.
Class features like the animal companion and undead cohort are duplicated by feats. And there's little point in having a animal companion that you can't buff.
Spell list is way too limited as well.
Compare the cleric to the death mage for example. What do you get? A more limited spell list, less armor, pale road and death bond don't really cut it. One of the death bond abilities is basically half the cleric domains.
Melee spellcaster that has no way to increase AC or damage seems silly to me (Reap is significantly worse than sneak attack, which is itself not very good). And it doesn't have the spells to stand back and support from the rear either (and if you are doing that, a cleric or wizard can do that and more).
Weakest combination is probably reaper mage + domain, you are a melee spellcaster with MAD and has to rely on hitting enemies to do damage with worse spells than a cleric.