You're right that the Klingons and Romulans had pretty much undergone a reversal by the TNG era, but it doesn't make sense to blame Ron Moore for that, since he came along after it had already happened. It began with The Search for Spock, in which the villains were originally written as Romulans -- flying Birds of Prey with cloaking devices and talking about honor -- but then got switched to Klingons without the script being substantially rewritten at all. That was the beginning of the association with Klingons and honor.
I am going to disagree somewhat with this. The Klingons of Star Trek III are still not Samurai-Biker-Vikings with no brains and an endless need to stop everything to settle honour debts. They are ruthless and vicious, but not idiots... for the most part.
In Star Trek V we see the TNG Klingon taint in full force... I mean the half naked bare chested Klingon BOP commander, his female body builder officer... etc... Then, thankfully, but Star Trek VI we are back to TOS Klingons, those wonderfully sinister bastards.
Notice none of them have ragged teeth?
John M. Ford's Klingons have always been the ones for me.