The shackles are really easy to see and it takes only a sprint to the player to remove them. The fire also seems to spawn in the same place every time. The fight is rather easy if everyone knows the mechanics. That fight is balanced accordingly. Just because you fail to complete it, it doesn't mean its "impossible." Its not even hard.
This. Any kind of cc breaker or movement impairment breaker works as well, so consulars and troopers are functionally immune to the shackles. Slingers have hightail it, making them functionally immune as well. Scoundrels have the cc breaker and dodge. Jedi knights are (IIRC) the only classes that only have the standard cc breaker to remove them on their own. That is really a problem only in the case the tank was tanking it in the wrong position and so you got knocked back and shackled in the fire TWICE in the encounter.