I made my observations based on your Overbuff comp stats.

Let me clarify with specifics.

it can mean you're not soaking enough damage for your DPS players

As D.Va, your dmg blocked is low. Your deaths are also low. This tells me you're either not taking enough damage to risk dying, or taking too much damage and losing your mech. In the former, you're not in a position to use matrix very effectively (too far from the fight) while in the latter, you need to retreat from the front line to stay alive. Also, your D.Va's weapon accuracy and crit rate are low. This probably means you are fighting outside of D.Va's optimal range (which also explains the low elims and low dmg) - which again, means you're too far from the fight or spending too much time in the back line trying to recover your mech. Either scenario means that you're not protecting your teams against the enemy.

Your Rein elims and dmg are really really low. Sometimes, as Rein, you need to fight. Don't just be a walking shield.

Your elims, dmg, shatter kills, and firestrikes are in the bottom quintile for Rein players while the number of deaths is at the 94th percentile. This tells me that you need to be way more aggressive during team fights. My guess is that, sometimes, your DPS players are initiating the team fight ahead of you and your shield - if that's the case, get in there and help them. Also, work on your earthshatters and following up with firestrike/hammer. If you shatter their supports, it should be an almost guaranteed kill since shatter+firestrike+hammer = 225 vs 200hp of Ana, Lucio, Mercy, and Zen.