Mr malty and dry yeast

I have always used mr malty.com for making starters using vials of liquid yeast. I made a 1067 beer 3 weeks ago and, based off of what mr malty said for DRY yeast, all I required was 1 yeast packet. At the time that seemed incorrect for a fairly high gravity beer. But I had kinda forgotten about the yeast up until then so, on a whim, I rehydrated and used one yeast pack. I have never had any attenuation problem before, but this beer finished at 1026. On the bright side it wasn't overly cloying, but way to high considering I needed to get down to 1011 ish. It was an extract batch so no fermentability issue. I aerate with the little aquarium pump and diffusion stone- which seemed to be producing less bubbles so I let it aerate for 45 mins. It's gotta be a problem with aeration or cell count. Does it make sense to use a single dry yeast packet on a beer of this gravity?

Yes, an 11 gram package should easily manage 1.067.