@tombond I'm not sure what you mean by 50%? Are you entering 127 for the laser max (which would be 50%)
You should be able to get excellent grey scale results if you have a TTL laser (the blue module). So something isn't set correctly, but I am not sure what.
Are you running my Grbl 1.1e firmware?
Restore T2Laser back to defaults (in the Help menu) and then use the grey scale test file, see what you get and adjust feed rate higher if it's too dark and lower if not burned enough.