One idea I have is to lower the "minimum cap" of attributes at character creation. Right now if I understand it, new characters start with 5 points in all 6 attributes that are fixed and unremoveable and 5 points to distribute.

As I've pointed out, for a fighter, they're looking at no fewer than 3 attributes that they must spread those 5 point between: STR, PER, and either SPD (to be an evasion-fighter) or CON (to tank). If they want to cast spells to take advantage of the magic combo system, add INT to that list.

To help, maybe let players re-allocate at least one of the 5 "fixed" points from their starting stats. That could help pure fighters, by letting them sacrifice points in Dexterity and Intelligence that aren't going to do them much good, and letting them be put elsewhere that's more useful. Maybe put a cap of 10 into any stat at character creation to prevent excess point stacking, if that's a concern.