Don't forget mash pH.
I could be mistaken, but I don't think pH has much impact on mash efficiency. You'll get better conversion efficiency for sure and better fermentability, and better beer overall. But if the OG is off by 15 points, that's a matter of starches being totally left behind, converted or not.
I absolutely agree that mash pH is quite important, and it should be something the OP looks at, but he's gotta get the starches (and enzymes) into the liquor before he worries about how well the starches are converting. In my early days I was hitting my pre- and post-boil OGs on the dot before I ever started thinking about pH.