Being the geek that i am, I just pictured a guy in some kind of kevlar/composite armor power suit with a bigass Gundam style sheild in his offhand for protection against heavier weapons, assuming that you had good reflexes and everyone only used heavy weapons from your off side.
Transparent aluminum research (which would be lighter and stronger than conventional bullet resistant glass), Johns Hopkins machinists do armor research for the military, MIT student’s work on making lighter armor, Ukraine gets in on the transparent armor act, Ballistic Armor Research Group, LLC. Lighter armor will pay big dividends (and no doubt much of the research on it is classified) as it enables you to better protect fighting forces, while reducing fuel consumption.
As for the joints, those will always be weak points, but much can be done to minimize the risk to them, just look at a suit of armor.
They should have given the contract to Stark Industries - the real leader in battle armor technology.
Fools! a force-field would solve all these problems.
Well, a forcefield would be just fine until some dumb doof decides to shoot at you with a Lazgun. 
Hokey religions and ancient weapons are no match for a good blaster at your side, kid
“Mecha-Sheba!”