I read all of those and never got the impression that they were Iron Man and doing aerial cartwheels in half-ton armor. They were always described as methodical and tank-like. They are fast, but deliberate and stiff.
This is like Avengers meets Cirque Du Soleil.
What about when was got his new and was forced to go through the course with with cortana for the first time. He was literally running away from a jet. Their reflexes are so good a falling object seems to be in slow motion. In this trailer they survive an in atmosphere drop (no problem for a Spartan and they have thrusters to soften the fall) then ground pound ( remember 1000+ lb soldier using gravity and thrusters to slam into the ground). Sprint at high speeds using thrusters again. Board a phantom and kill a few elites (something that blue team has done several times). I'm not seeing what the issue is they have always been extremely fast and strong.