Beyond the headsculpt, the other thing that people never seem to mention in terms of the overall look of the HT Luke is the tunic - it's more than a half inch too short and isn't baggy enough, and it's probably 50% of what you are looking when viewing the HT Luke.
I swapped it for a modded Hasbro tunic (the sleeve ends have to be unpicked to lengthen the sleeves, but it's pretty easy) and it looks great IMO. It has the length, the bagginess and flows pretty well. It actually saved me from reselling the figure because it has a lot more farmboy Luke vibe to me than before.