Another question: are You use a rule for reducing damage for wearing an armor with the Hack'N'slash combat system? Can You mix the reducing damage system from Martial Law with Hack'N'Slash (I think there's a important point to give an advantage for wearing an armour; I read from history books that in the Renaissance era [16 century] it was hard to kill a fighter wearing plate armours ("Harnois blanc ou plain" in French), some fire weapons cannot even pierce this armours ("? l'?preuve" in French).
In my opinion in
HARP DB =
Damage Reduction +
Evading Capabilities. So to me the DB from armor is already partialy damage reduction. And the game was balanced in a way to let
Heavy Tanks,
Quick-agile, or
Spell protected characters to survive equaly.
But if you want to ajust the criticals furter I strongly recomend randomizing criticals. Basicaly you will have the diference between the character that is a Tank and is hit often, but takes reduced the damage, and the other who evades a lot of attacks, but is hurt seriously when struck.
If you randomize Hack and Slash criticals, giving a generous "general passive DB" to everyone I believe that will do the trick, and you can combine both H&S and ML.
I have not play tested this but it is probably how I will randle criticals in my next campaign. I hope you like it and call if have more doubts.
Regards,
Andre
PS: One foot note on armors: every real ages of our history had a kind of "uniformization" of armors vessus weapons. But usualy in fantasy settings we love to see a mix of styles.
To give one example: In LotR we have the heavy armored Guimli, fighting side by side with Legolas and Aragorn. Would not be the like that if every warrior had only one good parth to follow. If you really like the idea of making heavy armor better than all othe options, be prepared for very heavy armored players in the long run.