Remove cores from infusion. Leave them for masterwork only. In fact make masterwork a more meaningful choice by having more customisable options; remove the multiple cores needed for masterwork and replace them with different types of cores for different stat improvements. Make them hard to get. Your design choices for the player to customise and keep using the gear they like, is outdated. Other games do this better. Getting to keep using the armour and weapons I like, without a pointless barrier to upgrade only their light stat, is a good thing. Apart from gambit and Iron Banner, the light metric falls under the law of diminishing returns. When you exceed the minimum required for an activity then everything is scaled. So why protect it behind this pointless grind. Grind and difficulty should be for those stats that have a powerful effect.