Skins & pack weight
One of the most difficult jobs in traveling with a pulk is attempting to go up steep terrain while hauling a heavy load. At the point that your ski wax loses its battle with the uphill slant, it is either herringbone in deep powder or switch to skins. Skins (which basically imitate the one-way grain of animal fur i.e. seal/ horse or mole hides) give the skier much greater uphill purchase.
Good skins attached on the full length of the ski will give you plenty of uphill grab for most inclines. As it gets really steep, or if you are using shorter kicker skins, you have to remember that by using a pulk, you have taken most of the weight from your pack off of your body and your skins now have to use the downward force of only your body weight to also keep the heavy pulk from sliding backward. In this case it may make some sense to place some more weight in your day pack to lighten the pulk and give you more downward purchase on the snow.
After attempting a large uphill climb there is little question that it is a real slog. Before condemning the pulk behind you, think about how hard it would have been to climb the same terrain with all that weight on your back. Besides, now that you are on top of the ridge and taking a breather with no load, remember that your buddy with the pack is still dealing with his heavy load.