Just a quick thought, if you are constantly running Sin and Jugg, get the Sin to deal with the adds. The damage from Grob is not hard to heal (if you think the Jugg is under geared) and a Sin will have much easier time keeping threat on the adds with Discharge used on cd. The idea is not to have the tank DPS the adds down but to simply take them to the lava pools, the adds die very fast if they are kept there. Let the tank even run through or jump across the lava. As long as he is not standing in it, he should not take much damage. I tank this by 'dancing' around the lava until all adds die and then get ready to hit the next group.
Playing into strengths and weaknesses of each class is something you may need to do as raid leader and if you are not sure there is wealth of information around.
Also I noticed that the Sorc is a clicker and moves camera with keyboard. While I am not going to go 'lol noob' it is generally a sub optimal way to play even if less crucial in PvE than in PvP. Try to have him practice rotation on a dummy only using key binds and see if that makes any difference to him and your group. His rotation is also a bit off, particularly not using Thundering Blast on cd which is where majority of Lightning damage comes from. Furthermore casting FL without proc, casting Chain Lightning without proc and using Shock rotationally as well a for some reason Force Slow on a boss with Immunity. All these mistakes add up and lower his potential DPS. Swtorboard.org has some excellent and detailed guides up on DPS.
Having logs from all DPS would help us fine tune their rotations too or at least see who is 'weak link'. In the meantime just have them look up either Swtorboard or Dulfy and see how far off they are from optimal rotations.
Healers seem to be okay but this is not a taxing fight to heal so hard to tell. I can't speak for the Sorc due to unknown usage of Static Barrier which lowers shown HPS/EHPS considerably (ST healing loss of cca 400 HPS when used as soon as Deionised debuff wears off, fully effective).
It is hard to tell if you are taking too much damage, but have a look at this
and see how close you are to those mitigation ratings and change your gear accordingly. You are also saying that you run with 78s. Provided you bought these with comms, the mods and enhancements are worse than 72 token ones.
EDIT: looking through the videos linked I would have to agree with BreakingNews that there is a lot of room for improvement for most people taking those videos. Again, just have them do some research on both their class and the fights.