Are trying to get on the small rock by the last lamp? If not I would try that one and if yes go right round it after starting the bridge sync plate so that you can see the lamp over the top of it; that has been the easiest side for me to jump on. I'm assuming you have taken all your weight off at the last lamp before sprinting to the sync play end then back towards the rock? And don't panic if you can't get up there first time, just get right next to it and try again (only press jump button once if you are already too heavy as double/triple jump won't work and you'll be cancelling out your jump if you instinctively double press it), you do have time for a couple more tries before the thralls will get to you. Once you're up there and have killed the ogre (now is not a good time to realise you have no ammo synth :;) just wait until the weight of darkness clears and then remember NOT to get caught by the couple of thralls that try to ambush you on the bridge. You'll get it!