Nice one Las, just watched a few of those vids and some useful tips. Already learned something about escort missions - the payload moves faster the more players are on it, but caps out at 3. Most escort matches it's rare to see more than one on it, but then everyone wonders why a team with Bastion (or Torbjorn) + Reinhardt + Mercy on the payload pushes through like a hot knife through butter.
The "5 biggest mistakes" highlighted in those videos was interesting, most of them you see repeated again and again and I haven't seen much change in this behaviour since launch, so it's going to be like any other objective-based PvP game, rather hit or miss from match to match. The average (random) player seems to still approach it as a death match rather than an objective-based game, run off solo, get killed, rinse and repeat.
Obviously grouping with friends helps. But even then people seem to forget about objectives in the heat of battle, stick to certain heroes even if they aren't working out too well and generally not stick together as a team that well. I'm guilty of all this too, it can be hard to keep track of everything and everyone in such a fast paced game. And it's very tempting to keep trying to make a certain hero work rather than switching. But I think sticking together should be #1 on the priority list. Most of the best teams seem to work very closely together, all watching each others backs and focusing down key targets.