I don't mind this "bug" and I don't want it to change. It is easily overcome. Mashing the same buttons and rotations over and over again gets old. A mildly complicated mechanic in a Hardmode FP is a pleasant change.
1. The demands on healing, dps, and mitigation for this fight are very low.
a. I've never seen anyone die from anything but the rocket exhaust (or the entire rest of the group dying from the rocket exhaust and the boss slowly whittling the last player standing down).
b. It isn't necessary to have two dps, I don't even think it is necessary to have one dps, but I am not sure. (Just because I have never seen him enrage doesn't me he never does)
2. Because the dps demand is so low you have an extra player that can be put on shackle patrol, when I am tanking I direct a melee dps or a poorly geared dps to do this and to not bother with doing any dps.
3. Because the healing demand is so low the healer can be back-up shackle patrol (mostly for situations where the player on shackle patrol gets shackled)
4. Other than when you have to unshackle someone you do not need to move very often ( the rocket exhaust does not change places at intervals of less than 30 seconds)
a. Once the tank is in place with his back against the wall nobody NEEDS to move until the exhaust moves to the sector they are in
b. some abilities that break the root have a shorter cooldown than time between the rocket exhaust movement so you can actually completely ignore the shackles with some group compositions as long the healer and one other player have such an ability and enough brainpower to hit that button when the rocket exhaust demands they move ( i.e. Troopers Hold the Line on a 30 second cooldown which also helps you to get to the new sector faster with the speed boost )
Your dead on here , everyone needs to have backs to the wall , and SPREAD OUT for christ sakes!!! Melee use ranged abilities then EASE INTO DPSING , if you zerg rush him with melee he will shackle. Melee stay 5m and after rotation BACK OFF!! In several groups I've witnessed melee just zerg right into him, tanks that kite him around like wild chickens , and healers that don't know to break the shackles. People , you have to stand still , spread out , and take it easy with this fight. You follow this method the FP becomes very easy .......