When u play barik make different loadouts for turrets, shield, demage and try to counter the enemys build. Try to make uncounterable loadouts, for example do not make a loadout just focusing on turrets cos thats easy to counter with bulldozer card.
Grover's ultimate does not make him CC immune but stunning him will not cancel the aoe heal. Displacement heavy comps are very powerful against him since they can keep him away from his team and reduce his healing.
Try to do a dubble jump, pounce upwards, tripple jump, nine lives, punce, quad jump combo. Hit ur daggers and win the 1v1, unless its hitscan or a counter. If that play safe. If the enemy is spread out or someone is low, try to outflank the enemy.