BW's ability triggers when she's assigned to attack, so each die would do 2 damage to the opponent right away - before they even have a chance to declare any blockers.
If GG is fielded on the other side, he'd trigger 3 times, enough to KO all the Tsarina's.
In this situation, Hulk is still available to block as only his ability has been triggered so far. If the Tsarina's were the only dice declared as attackers, then the turn is basically over as there would be no need to declare blockers or assign damage beyond what the triggered abilities have done. IOW, there is no combat damage because the damage and KO's happened before combat actually started.
tl/dr - active player attacks with 3 Tsarinas immediately dealing 6 dam to opponent, triggering opponent's GG ability 3 times and KOing all 3 BW dice.
This is 100% correct.
Devil's Advocate: Would either player still have the ability to use Globals?