Can you give me some advice on how not to suck at ninja?

Hey guys, I am kind of new to this game and to mmos in general.
I completed the main storyline in easy mode Bard and I created a new ninja character and it's more complicated than I thought. I am okay with dps and combos but I have a huge issue since I started these lvl40+ dungeons, I always die during boss fights, sometimes more than once. I am lvl 50 right before the ultima weapon dungeon and I'm too scared to go there because there are so many bosses and I don't want to die lol.

So, how should I position during boss fights? I make sure that my tank always has aggro on him and I can dodge the orange skillshots, but it always seems that I die to the boss' random aoe, I get hit even if I'm attacking from behind and I never see it coming. Since I am the only one in my parties to die like this I am doing something wrong and I don't know what. Can I have some advice on how to avoid that damage? It would be greatly appreciated.

Don´t get cleave front of boss.
Check you debuff on you status bar.
Do correct with mechanic.
check boss castbar some AoE from Boss don´t have orange cicrle at ground. example: Chimera voice of Ram or cyclops 100-Tonze Swing
If you still die that´s healer fault.

Melee usually stays behind or sides of boss. Depends on positional requirements of your skills and those projected fields to dodge. Standing in front of boss you will most likely eat cleaves all the time, don't do that. Generally in an MMORPG you will need to learn fights. You either watch a video or play fights a few times to that end. Sometimes it's boss mechanics that need to be played correctly, other times attacks are simply targeted at you and cannot be avoided, if you die to those you'll want to upgrade gear for more vitality.

However, do not fear death. Do not be scared to go into dungeons. You will die a lot, ok. And you will die stupidly, we all do. It's not bad. At least not as bad as a few foul-mouthed players want to make you believe. Death is a learning mechanic, one that says "you did that wrong". But now you know! Next time that attack won't get you. You learn, you win.

BTW in FFXIV you can have all classes on one char; no need to create a new one for another class.

Oh, that have nothing to do with Ninja...

But don't get upset with the MSQ-dungeon (that with "Ultima"). People tend to rush it, because SE did some mistakes there (many cutscenes) and most people are impatient.

So if people yell @ you, don't listen. But you may be forced to decide between a) taking part in battles or b) watching the cutscenes (can be rewatched in the Inn).
In later dungeons/trials/etc. SE did better by showing most cutscenes only before and after content (most people are still impatient though ^^).

Thank your for your answers, i'll try to work on some things. I am too focused on my skills timers and I may have neglected the others information on screen. And I guess I'll have to learn some boss tactics as well.

Oh, and with the new TP bar, now you know when to use your Goad at better times. Both your Bard and Ninja should be happy.