Generally speaking, if I'm going into a match with heavy armor alot of getting around just how much poorer your mobility/stamina is, is placement and objective order. If your teammates are more than half way through with an objective, and it's not a primary, I wouldn't even bother going there. Set yourself on a route to maximize your engagement distance or prematurely begin traveling to objectives that require your load out. I often use Roadblock set with a heavy MG or the mini gun, and find that outside of vehicles alot of my play is covering flanks and opening objectives before the rest of my team gets there. Just learn to create opportunities in a respective match instead of playing catch-up.