Am I right to understand that your process was: Dregs->800mL starter->decant->800mL starter->now ?
If so, I don't think I would call that enough for a relatively big beer (1.070 is borderline "big beer"). My system is usually slant->10mL->50mL->500mL-> 1-2L depending on the size of the beer. If I am doing a tiple or something (1.080 and up) I will even add an extra step of 1-2 L at the end. I will do a cell count right now on my latest starter and post back with how many cells that gave me.
Edit: Just checked, and my steps of slant->10mL->100mL->1000mL->Decant->1500mL gave me around 120 billion cells. About 1/2 of what I need for my 1.080 Belgian.