I have an idea that hopefully makes everyone happy.
1. Make cores have the ability to re-roll the masterwork on an item for 10 cores or have the ability to change once perk once per gun for 10 cores. Both can be done at Banshee.
2. Make masterworking cost 15 cores.
3. Remove cores from infusion or significantly reduce the cost to infuse.
That way, there's still a reason to grind for cores so the core economy doesn't become essentially useless. And even better, I won't have to get on the forums and read "REMOVE CORES OR I'LL DELETE THE GAME" posts every day. Getting real tired of it. This game is so much more than little orange stones.