For me uniqueness comes more from the way I am able to play with the abilities, tools, and gear I'm given than from character creation options. I like the sort of gameplay tools where someone can say "I want a tank that likes x, y, z for this dungeon" and think of a fellow player that fits that description based on how they use their abilities, reagents, and gearing.
One reason I was drawn to the original IP was the design concept behind the mastery system, which appears to be getting some of that "player identity design goal" implementation in Embers in the form of reagent augmentation. Weapons so far have some modest differences that hopefully can be further improved with iteration, especially with positional values, weapon damage typing, and pen/dam/hit values eventually being distinguishable by the end user.
What does all of that mean? I'm a currently a MAR tank that likes to tank, pull, and cc, all at once, so I try to set up my gear and my abilities towards that playstyle and so far I've been able to do it to some degree. LAS means making choices so some skills are a must and some skills have to be left behind; the key is being identified as the tank that likes to do those things and functions in that role compared to other MAR tanks who may only prefer to tank and cc, tank and pull, cc and pull, or also likes the trio of actions but does them differently. When I'm in a position to do the trio of activities I mentioned, group mates will be made aware I will not have a provoke on my bar in order to have abilities to cc and pull., so I may lose aggro at times and not get it back as fast. Groups will notice I'm far more willing to toggle between sword/board and my 2h based on aggro, and astute knights have learned to aggressively use enraging strike on CD even if I'm primarily the one holding aggro to allow me to go ham with positional damage to build even more aggro, and everyone accounts for the soft ping pong moments with their own positionals.
I have had groups with 2 MAR and both played completely different, and communicated when it came to overlapping skills to make sure they didn't overheal. I've had 2 brigs in my group both playing completely different, even to the preference of which cc (stun or daze) they preferred to fire off first. That's showing potential for people to play the same specs but maintain a personal identity.
If people can see other players playing the same classes with very different outcomes and methodologies, that's being unique.