While I believe most compositions are viable, specially on low ranks, people seen to need a Reinhart on the front to function. Note having a Rein doesn't means they stay behind him, Rein is there to give the enemy a target to shoot and IF the enemy team choose to ignore the big guy with a shield you can see the team fold like a castle of cards.

However, if the enemy has a Roadhog, the only way to capture a point is to have a Rein. Don't give me crap about "bait the hook". If you are smart enough to bait the hook, the Hog may also be smart enough to not be baited..

If the enemy team has a Roadhog and your team has no Rein, being out of the spawn is being out of position basically. Yeah, people should swap, but Soldier has 12% ulti already, he can't change now!