Yeah, without a bit more info its hard to specifically answer your querry. So here generic advice, and hopefully some of it is useful. Most important rule: Dont run ahead of the tank and only attack the mobs that theyve already angered. Stay close to the group so the healer can reach you if needed. AoE on groups, single target otherwise. Dont be afraid to tell people youre new to a dungeon or ask for help understanding a mechanic you dont get. If youre playing on PS4, investing in a cheap keyboard can do wonders for your ability to communicate. The higher level you get, the more important it becomes to avoid enemy AoEs when you can.

Now some generics that are specific to BLM(the above applies to everyone). The break-even point for your AoE rotation is basically 3 enemies. With that many or more you get more damage from Fire 2 and Thunder 2 then you do from the alternatives. Have you learned your stances? Astral Fire is your damage stance, Umbral Ice is for recovery. Ideally you get a fully boosted AF(3 stacks) with an F3 cast, repeatedly cast F1/2 for your damage until you run low on mana, then use B3 to switch to UI(gives you all 3 stacks) to regen your mana(apply/reapply your thunder DoT while regening), before using F3 to get back to burning. If you mess up the rotation and dont have enough for a B3, you can still use Transpose to switch and start the regen going. Also, look at your role skills. You always want to have some set to make your job easier. As a BLM i always have swiftcast set, and i almost always have diversion and lucid dreaming set for aggro management. Personally i round out my load out with mana shift and apoc most of the time, but surecast addle and erase can be useful(or amazing) in the right situation too(break theoretically too for the long-ish duration heavy, though i dont think that situation is currently in the game - at higher levels drain is too weak to be all that useful). And dont forget you can hit manaward to negate or blunt some incoming attacks when needed.

And if you were looking for specific boss advice for that dungeon, heres a couple hints. Basically, youre re-taking a fallen keep from the dragons that moved in. So dont stand in front of them to avoid breath attacks. During the second boss in particular, a dragon shows up outside the window to cause trouble. Use the cannons in the room to scare it off so you can fight in peace. And just generally, avoid aoes and ground puddles left behind.

Editors note: I went to check your gear to make sure it wasnt part of the problem, but it looks like you logged out on weaver most recently so my character search proved not that helpful.