Remove the shackles from HM Cademimu. It the makes FP practically unbeatable. I mean what are you supposed all 4 people get shackles? Or everyone is given shackles and then knocked into the fire.
I strongly disagree with any opinion that one of our few precious 55 flashpoints need a nerf. We only have 4 of them to entertain us and the last thing anyone should want is make one of them more boring. if one of them is challenging your group, be thankful to the developers they made it interesting!
concerning your particular problem, with practice the shackles will become more of a fun mechanic and less of headache, they are totally doable as a pug. i found the wookiee/ugnaught fight to be harder without proper strategy.
everyone needs to stop calling for nerfs or else we will all be sad when they do nerf it and it becomes boring.