Let's look at some of the defining traits of each hero:
Valla
Fragile Hero
Tons of damage, both burst and sustained.
Mobile kit and hard to kill in the hands of a skilled player.
Best defense is usually a good offense.
Tassadar
Low Damage and no CC tools.
Best paired with auto attack based heroes thanks to Leeching Plasma.
Auriel
Requires steady stream of damage
In return, outputs incredible heeling
