pfr but I suppose my laptop is going into some kind or hibernation state when left for a long period of time. If I wake it from sleep after a minute or two it works, but if I leave it for 10-15 minutes it will wake will 100% brightness.
Since you don't run a DE, it's more likely that DPMS kicked in. And then, when the kernel turns the LCD on, it sets the brightness back to 100%. You should be able to see the DPMS timeouts with:
$ xset q | sed -n '/DPMS/,$p'
DPMS (Energy Star):
Standby: 300 Suspend: 600 Off: 900
DPMS is Enabled
Monitor is On
$
Until the kernel DRM driver is fixed--and if you run an external locker program--you can create a shell-script like this and run that in place of the original locker program:
$ cat ~/bin/scrlock
#!/bin/sh
export PATH=$PATH:/usr/pkg/bin
original_screen_locker
intel_backlight 85 || true
$ chmod u+x ~/bin/scrlock
$ xidle -area 10 -delay 3 -sw -program ~/bin/scrlock -timeout 300 &
This should do the job.