Hi,
So after playing for awhile with Necromancer I feel the need to bring this topic back up again → Archamge and Dread Phalanx.
Zarono has a very good point, if you play necro minion build, its almost useless or no point at all to take Archamage and/or Dred Phalanx. The damage gained from picking those node is incomparable to just having more minions. More minions translated into more dps AND more proccing effect e.g. armor shred from necro passive tree.
He already suggested some ways to fixed this problem in his original post and I think I agree with his suggestions.
The only way to make the Archmage node useful in its current state, is more on the quality of life and gearing. You can use Dreadshade skill pick the cast on minion node, 100 crit chance node, and +100% damage node. With 1 Archmage, you don’t have to recast it often and also you can focus on other affixes on gear rather than skeleton crit chance e.g. skeleton mage damage/minion fire/cold damage. Still I haven’t test this idea in terms of damage output. Maybe it could work but I still doubt it will out dps the more minions approach.