I'm 6'2" and, like most people who front squat properly, feel it fatigue the upper back much more than the lower back, in addition to quads and abs.
I'm betting it's more technique-related than anything else. Front squat is almost designed to involve the lower back less, when it's done properly. Make sure you have the bar super-close to your throat and keep the elbows high the entire set. If you're doing them for moderate to high reps (a few months back you wrote about front squatting 4x8-12), you're probably letting your form slip.
How are you programming them - what weight are you using for what set/rep scheme?
For context, what are your current bests on the back squat and deadlift?
Going "too low" is rarely a legitimate problem for most people.
Are you up for posting a form check video?