For overall strategy/adapting video tactics I mostly try to identify if the map mostly favors a "shooting gallery" approach with only light blocking (and by extension minimal healers) or a choke point strategy complete with low dps support units like heavies and healers. I say this because while it's tempting to look at your final formation and say "But Kayfabe, by the end of the map I'm using both blockers and shooters!" it's important to realize that on many maps there's an intermediate phase where your team comp should probably be leaning heavily one way or the other.