I made a "Minion"-like rule by just reduce HP by half for my Iron Heroes game. But that was before any details on the Minion rules existed.
Today, I might make this work differently.
CR -3:
1 HP, Evasion, Mettle. All damage is average, and Minions cannot score critical hits (but automatic hits are okay). (If they have a special ability like "Augmented Criticals", you might allow them to do so on a 20)
For monsters with Save or Die/Suck abilities: Remove them.
If you really want to keep them, require 2-4 of the Minions to work together to replicate the effect. (So, you might need to see 4 Bodak Minions to make a Save, and maybe 2 Ghuls need to hit you before you need to save for paralysis.) Or it simply takes more rounds for the effect to work (after 4 rounds of looking at the Medusa Minions, you turn to stone.).
Both ways increase the urgency of dispatching the Minions.
The big problem in 3E will be that at high levels, missing a Minion is highly unlikely, but at low levels, it will happen often.
Therefore maybe the still should have hit points, but only a lot less (1/2 or 1/3 is okay). Keeping Evasion and Mettle might still be a good idea...