The biggest problem with pugs is finding a group that will stay more then 3-5 wipes and finding one that does your strategy. It can be done though, just expect it to take a whole lot longer to learn and progress in one. You will get some groups who are incapable of learning mechanics, some groups where you will have a person parsing who complains non-stop everyone is not top parse in a learning party, some people who lie about their progression in a fight who know nothing about the mechanics, and you will find the rare groups that will work on learning the fight and actually get stuff done.

A static is 1000xs better as people usually stick together while learning, stick to 1 strategy, usually a whole lot less toxic, and are in coms which makes learning so much more effective. I would recommend getting a static for anything above EX primal fights, but it is doable without it.

When you start learning a fight your dmg will probably be really bad because you are learning mechanics and not focusing on dps at all time. That is sorta expected. As you learn the fight you learn how to weave your combo in and out, when to pop what buffs, and how to maximize your rotation in the fight. The fights in FFXIV are 100% the same everytime with maby a slight variance in order. So once you master the fight and rotation you can really fine tune it.

When you get into harder fights just find a party finder where you are in terms of progression into the fight. Usually fights are broken up into blind learning, Adds, phase 1, phase 2, ect progression. Just remember if you can kill the dummy for the fight your dps is technically high enough, just need to learn the fight and your rotation in it and you are good.