I'm guessing that you mean that you were running two 8 cell packs in series and it was only drawing from one pack. Is that what you are saying? If so, I don't see how it was drawing at all. If you were using a series connection between the packs, and there was a bad connection some place, you'd have an open circuit and no current would flow to the esc.

What makes you say that the esc was only drawing from one pack? If that is the case, then you may have mistakenly set the packs up in parallel; and, if that is the case, you may have been drawing more current than the esc could handle. IIRC, the GP3300 can dump some serious current when fully charged.

16 nimh cells in series is good for some pretty high voltage and there are a few that run that many cells. I just don't have any idea of the current that your setup will draw.