Using a shock pulse focused loadout, Grohk can frequently slow down and damage groups and even hurt fragile champions behind cover. Use hard shields (Barik, Fernando, Makoa) frequently to protect your team.
Shock Pulse will bounce if it hits a deployable like Ying's Illusions or Barik's Turrets. If you are playing competitive and he is picked early, avoid using these two to make Shock Pulse more difficult to use.