Temperature of the pack has to do with how much energy your pulling from them. In 2wd buggy the pack will not really get more than warm. In 4wd SC they will get warm/hot. This class shouldn't really be run on 2S in my opinion as it's allot closer to 1/8th scale than 10th scale.

As far as the distortion of the packs go this is normal as the cells fully use up the inside of the case so the 1.5mm plastic will distort. All Lithium cells will expand and this is normal. In fact in an article I read awhile ago even cell phone manufacturers leave some room for expansion. Lower mAh packs with lower C rates will not show this as much as there is extra room in the case to allow expansion. The high end packs with maxed out C rate and mAh will get slightly rounded as there is no clearance inside the case. The cells are built at 5.5mm and there is 4 cells in a pack so this is 22mm and the case is 25mm once built this leaves 1.5mm for the case thickness.