ToBeFrank

Noah starts as an Attacker and has many S- and A-ranked Attacker classes, but inherits two of the four non-starter tanks, showing his willingness to lead from the front to protect others.

Mio starts as a Tank, but the vast majority of her S's and A's are in Healer classes. It's a hint both to her heritage (Nia is one of the most powerful healers in Alrest) and her kind nature.

Eunie's starting class is a Healer, but to nobody's surprise, she favors aggressive Classes like Lone Exile, Full Metal Jaguar, and Seraph. It's strongly implied that she was an Attacker before Joran's death, and she somehow became a Healer to make up for it.

Taion doesn't heavily favor one type of class, matching his strategic and flexible mindset.

Lanz appears straightforward and blunt, but a lot of his high-aptitude classes are healers. He's actually quite gentle and intelligent under his bluster, as we see in his softer moments.

Sena is a fairly straightforward Attacker, much like she is, but having high ranks in classes like Machine Assassin and Stalker likely reflect how she keeps her true feelings hidden.

(Spreadsheet I made to look at all class ranks below the cut. Because I couldn't find one online.)