That's because you're only level 27. Below 50, there's almost never a reason for a tank or healer to use their limit break unless something catastrophic happens like undergeared people going into Garuda and cannot survive The Reckoning then you need tank LB. I think Yoshi intends for the game to really start at 50 which is where you see different LB at different level being used. DPS is still the most useful to lessen time on dungeons and bosses. And for Ifrit if you don't have AOE LB, use single target LB3 on 1 nail, focus on 2, use LB2 on the last one. You'll burn it down just as he jumps up.