Deck 1 - Base Damage Deck -- The selection of the card for this would work exactly like you describe in your first paragraph.
In my proposal, the player would still do an attack role using the appropiate weapon chart. This would give base damage and crit (when applicable). The player would then draw from the Base Damage correct deck (i.e. the puncture crit deck). Cards will have rows -4 to +4 just as described.
The only change being what is marked in Green.
To this, we also add....
Once the Base Damage Card has been selected, we also select the card that is appropriate to the type of critical.
The same exact method is used to determine which result to use from both card as they are both laid out in the same fashion.
Base Damage Card might look like this:
-4) Week hit to right arm +1 hit.
-3) Hit to right arm +2 hits.
-2) Hit to right arm +4 hits.
-1) Hit to right arm +5 hits.
0) Hit to right arm +8 hits. Bleeding +1 per round
+1) Hit to right arm +9 hits. Bleeding +1 per round. Stunned 1 round
+2) Hit to right arm +9 hits. Bleeding +2 per round. Stunned 1 rounds
+3) Hit to right arm +12 hits. Bleeding +3 per round. Stunned for 2 rounds and at -20% for remainder of combat.
+4) Hit to right arm +15 hits. Bleeding +4 per round. Stunned and unable to parry for 2 rounds. -30% for remainder of combat.
And the Crit Type Card might look like this (for this example, the crit type is Slash):
-4) +3 hits
-3) +3 hits
-2) +3 hits
-1) +5 hits
0) +6 hits, +1 hit per round
+1) +7 hits, + 2 hits per round, +1 severity of existing stun (i.e. stun becomes stun, no parry), additional -5
+2) +8 hits, + 2 hits per round, +1 severity of existing stun, +1 stun, additional -10
+3) +9 hits, + 3 hits per round, +1 severity of existing stun, +2 stun, additional -15
+4) +10 hits, + 5 hits per round, +1 severity of existing stun, +2 stun, no parry, additional -20
So...
You roll get a 14 B crit (+1). Foe is wearing chain armor (-3) for a total adjustment of -2. This gives us the results
Hits to right arm +4 hits (Base Damage Card)
and
+3 hits (from the Crit Type: Slash card)
Which makes the attack to a total of 21 hits (14 + 4 + 3).
If the foe had been wearing no armor, the results would have been (presuming the same result on attack table of 14B) as follows (adjustment of +1 for the B crit, no adjustment for armor)
Base Damage Card: Hit to right arm +9 hits. Bleeding +1 per round. Stunned 1 round
Crit Type (Slash) Card: +7 hits, + 2 hits per round, +1 severity of existing stun (i.e. stun becomes stun, no parry), additional -5
Gives us total damage of: 30 hits (14 + 9 + 7), bleeding 3 hits per round, 1 round of Stun, No Parry, and -5 to all actions.
Is that any clearer?