I saw this problem on day 1. The game encourages similar builds because characters are generally available to everyone at the same time. Unique/good (and even some lower level) characters need to be available randomly to different people (not necessarily to everyone!).
Perhaps I'm biased, coming from Summoners War, but that game had the unique collection aspect nailed perfectly. Even a level 2 player could get a powerful character (as rare as that was). And each character was unique between players, because the "gear" (called runes) was customizable. The gear itself was variable. Sure, there's a chance that you may never see certain characters in Summoners due to the randomness of the draw, but that's what keeps players invested and yearning for more.
I know this is Star Wars and not Summoners War, but I really hope they implement (better!) ways for each player to make their account (and perhaps even their characters) unique.