Sore hip flexors mean they're being worked. That's because the hip flexors counteract the hamstrings which would cause posterior pelvic tilt during the lift. Posterior pelvic tilt at the bottom portion of a squat/OHS will cause rounding of the lumbar spine. So yes, you want your hip flexors to be working -- they help maintain the lordic curvature of the lumbar spine and keep the pelvis anteriorly rotated). That's probably a lot of volume if they're constantly sore though might wanna take a few days off.
If you're concerned about them getting too tight then you need to stretch them.