Why not? It's big clunky armor. You should be slower, and less accurate, in my opinion. One, you're coated in metal, and even with the assists, moving around shouldn't be perfect.
On a battlefield, mobility is life. Any armor suit that significantly slows down its wearer is worthless. This is, incidentally, one of the reasons that Dragonskin body armor IRL is such utter crap.
Two, try putting on a suit of armor, knight style, and running a course and dropping several targets accurately along the way. Doesn't seem very possible.
It is actually very possible. Medieval plate mail was heavy, but it distributed the weight evenly over your body - it was possible to both mount a horse unaided and do
cartwheels in plate mail armor. This is one of the things Hollywood got completely wrong - the only suits so heavy that they infringed mobility like that were jousting suits designed for show and certain ceremonial ones that would never actually be used in combat.
And plate mail doesn't even have a power assist to carry its own weight like Fallout PA does.