In a group its often a bit lame having followers or long term summons as you kind of steal the role of the fighters in the group was especially the case with OP druids or even Summoner special classes in 3rd edition. In a game its easily OP when the disadvantages of said spells like you would have as a necromancer are not fully employed by the system.
In P&P, i generally simplify the rules. Example, if i have 30 skeletons, and each one has 50% of chance to hit(need to roll 10), i assume that 15 oi then hit and they dealt average damage. To not spend minutes calculating each one... As for stealing the roles of fighters, what if the group has no fighters?
PS : Necros on 3.5e had OHK spells like Finger of Death/Wail of the Banshee and could have far more powerful creatures than zombies and skeletons...
IMO on computer games, the games with the best necromnacers are : - Arcanum - Pathfinder Kingmaker - Diablo 2 - Might & Magic VIII - Mount & Blade - Phantasy Calradia mod - Gothic 2 - Returning addon - BG1/2 (non EE)
This is what a necromancer able to cast circle 3 spells can do on g2-returning. Except by the dark mist(circle 6 - in scroll), i only casted circle 3 spells.
A Thassalion Gluttony (Necromamcy) Wizard Lich will blow all the other Necromamcers way when Wrath of the Righteous comes out.