as seen on the gameplay videos, you don't use energy for jumping high or meleeing, just for cloaking(over time), armoring(over time and when taking damage) and sprinting.
Those players don't know how to use the suit

http://www.youtube.com/watch?v=Vv1VkmbgnOs&t=1m7s
I've linked the Hero's Journey trailer to a moment where he's merging suit modes.
Look at the energy drain slowly over time from Armour, and when he starts sprinting it drops very, very quickly.