In summary,

or something like it, I believe people are saying if you want tons of production runes it's best to farm with alts. Main reason being your main is generally going to be maxed and the difference between production drops from being over the mob level compared to being 5 levels under is tremendous. I use 5 because I believe there is a slight drop off at 4 levels below, but as an example, 5 levels under, in a place like Land of Malevolence, with increased drop rate but tremendous amount isn't necessary, you can with ease get 1000 to 1200 blend runes in one hour. I am not exaggerating, and I manually loot all my drops, so it's very conceivable to get higher than that.
On the production rune drop rate in Salioca Basin in comparison to other regions I have no opinion.