As I see it, The Dev team has done an incredible job in balancing the armours in the game. While full-plate isn't as awesome as it used to be, it's still retains it's usefulness for people whose Dexterity does not exceed 12. Which, to be honest, are few and far between, but we still have heavy Clerics and Fighters out there willing to use them.
I'm not sure if anybody noticed, but it looks as if all the armours now have a total of +9 for AC between Max Dex and the actually AC bonus. What I mean is, Full-plate gives +8 AC and has Max Dex of +1, Studded Leather has +3 AC and +6 Max Dex, Half-plate gives +7 AC and +2 Max Dex so and so forth.
So, from the looks of it, I believe that the heavier would in fact see more use with the modifications since one can benefit from a high Dexterity without being gimped like you would in normal NWN or being forced to use Full-plate for the better overall result.
Just my two cents...