I am not saying I have the answer, just offering some help.

Ghaz is mostly a few tricks. No adds. Make sure you clear out where you will fight him (I usually do the end area where he walks out). DONT turn him or move him or he might get you close to another group and add them. He throws you so be ready for 1000-1500 damage. That is a lot, so be ready for healing, healing is key on him. He ice blocks someone, but not sure who, so be ready for a cleanse. You might try a bubble and remove bubble macro followed by a taunt so you can get out almost anything. It should be something like CancelAura. I am a defensive person, so I would judge light on him so each hit heals you. Maybe even seal of light to help even more.

The Chief? Guess that is the guy after the stairs. He drops aggro, but not sure why. Just be ready for it. I usually focus on his friend and then just focus on him. Be ready on mages to iceblock to protect if comes at them. Not really a good way to do that, just all iceblock at the same time or reach over to that chars keyboard and hit a key. He hits HARD, so I would be defensive again, judge light and seal light also.

Don't feel bad though, once you learn how to do things, they will be helpful later (ST boss throws, ST boss drops aggro, etc). And you are learning how to use your group make up instead of just getting free leveled up and not learning what to do. Keep it up. Good luck.