Honestly? NPC on NPC combat is a slog in any edition - and it's worst in 4e and 5e because in both games characters are complex and combat is asymmetric with NPCs having more hit points and doing less damage than equivalent danger PCs.

TSR D&D (including oD&D, B/X, BECMI, 1e, 2e, and the Rules Cyclopaedia) are all based on a hacked tabletop wargame where you are expected to manage squads of troops and the rules for NPC and even PC combatants are extremely simple, with minimal mechanical variety. Low level PCs were expected to go into the dungeon with a dozen or more followers between them with little more in the way of stats than a name, equipment, and a hit point total. OSR games frequently keep this aspect of D&D while removing some of the really clunky mechanics. I hear that Old School Essentials is the current favourite - or if you can handle some jank the Rules Cyclopaedia is what you want.

All 3.5 editions of WotC D&D (3.0, 3.5, 4e, and 5e) on the other hand have taken the assumption that you will not be handling a whole lot of hirelings - and because of this have ramped up the complexity of PCs and NPCs alike. 3.X had symmetric PC/NPC design which is a pain for DMs but helps this kind of game - and they all had hit point bloat. 5e made things asymmetric leading to a padded sumo. And 4e played up the synergy and tactics between party members meaning there could be emergent complexity. In particular the AoE effects and forced movement flying around lead to interesting tactics ... when you have 4 or 5 PCs. And minion rules for NPCs that are severely outpowered by the party are a good thing - but minion on minion combat gets silly.