At least in co-op. 30% of the time I join the game either on the last objective, or the last attempt at taking the objective which fails resulting in me spending a lot of my time only spectating people and not even spawning at all. It's very annoying. I also often miss the first spawn because I'm either adjusting my equipment or the game took so god damn long to load. (Why does it do that? CPU is only at 10% when it loads and it hangs up >.>)
Let people spawn when they join in-progress game even when there's no active spawn wave.