| Lexen_Rapier |
Personally this reads to me like you're making a mistake in cr's rather than needing to tweak the system necessarily.
A bunch of level 4 heroes can cut through many cr 1 minions, with very little threat to themselves - and often 1 hitting those mobs.
A cr 3 monster on its own probably won't kill a level 4 character except on a critical hit. This is a problem in general with critical hits at the low levels - if you had a cr monster crit a wizard for instance, they'll risk hitting negative hit points. (1d8 + 2, x2 vs 6 + 3d6 hp as an example).
In the same vein if you give the cr 1 minions heavy picks (1d6 x4 critical) they might well 1 shot a level 4 wizard. (4d6 vs 4d6 :P) - on the other hand this shouldn't happen that often with a level 4 party.
I'd consider re-evaluating your assumptions about this before changing the cr's and hp pools myself. However, if you want to go for a more pulpy game, making 1 hit mooks can help to create that effect.