Do the Assassination mission on Venus a few times - bursas are guaranteed to spawn up in the balconies, so if you get lucky you can finish that task in one run.
They fit you with a restraining bolt, which makes you do less damage to them/take more damage from them the next time you meet. Lotus will give you a blueprint to remove it though, so its really just a temporary debuff that probably won't have any effect.I also ran into the Grustag 3 again, but this time they beat me, since I was solo. Do they do anything besides embarrass you if they win?
Losing to the Zanuka Hunter, on the other hand, are where things start to get.... interesting.