As player that cameback , i feel the pain too, it took me for example 4-5 DR to not even die once and even then u make mistakes. watching guides help but u need to practice.
FFXIV is a different beast in raiding , and once u get the rythm u will IMPROVE A LOT , is not like other mmorpgs tbh. But to get to that point u need to PRACTICE. and dummy wont help u outside helping u on opener.
Every boss is different , u need to adapt to it , maybe use the CD sooner o later , party buffs are the most vital , if u dont put your "dmg" on the party dmg window your dps will suffer a lot. And to do that u need to adapt to your party and the boss.
First thing in FFXIV raiding is learning the boss , if u die or get hit by mechanics your dps will suffer, if a party member makes a mistake and kills u , your dps will suffer. To "not fail" u need to do the boss over and over , the issue is that it takes time and in FFXIV 1 player mistake is huge and can wipe or invalidate the try (pt doesnt die but boss gets a dmg buff so next raid wide probably kill every1)
once u know the boss timing your Cds accordinly to that boss maybe goes inmune too soon or a mechanic can interrupt it...but usually ffxiv raid bosses are dummys for a while so ppl can do the opener with easy.
FFXIV is mostly about patience , FFXIV mechanics is like learning to ride / drive , u have to remember so many things, mirros , seatbelt , the clutch , ect , but once u learn that driving is as natural as breathing and then u can improve your riding/driving to max.
About your static , why they didnt talk to you before ? u killed 2 bosses with them , 2 weeks and not even a word ? hell the RL should have talked to you in private or the other tank asked if u need any help , they knew u were new to ffxiv and savage.
Maybe it wasnt about you , maybe they got a friend wanting to join and u just were the new guy ¿? who knows...
But dont feel bad about it , get another static for EW , is a fresh expansionso time to catch up .