Try starting your fight with - Slow time > mind control > force breach > project, along with as you see fit, Saber strike and double strike, with kinetic throw every three stacks - whirling blow does not use any force so use it when low on force.
Hmmmm ...... lol ? Using a taunt as 2nd spell = noob. yes, noob.
Kinetic Ward just before engaging
Engaging with Force Pull during Force speed to reach the boss
And now, if you want to be SURE to keep the boss, Mind Control, but you probably don't need it, unless your DPS are overgeared and without guard.
For the OP : probably the healer's fault. I saw many Sages doing some DPS on that boss, just because the tank's hp are over 70%. 2 hits later, he dies.