If you get immobiled by his mystery, gakido can clear that immobile just like every other healer/debuff disperse character. If you cast your shield first and then Obito uses mystery on shielded target, shield and immunity go to waste, so time it right. If you want a counter, place in front of him ninjas that have a guaranteed hit (sage naruto clone barrage) to deal dmg or use less meaningful mystery/aoe standard attack to proc his dodge, mirror genjutsu works as well as means to counter immobile itself.

Your strategy (r1 hidan burst) will fail miserably, Obito's mystery clears all buffs/shields and immobilizes on top of that.