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.
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.