how can i unlock midas savage?

i've already completed A Gob in the Machine quest. but the wandering ministrel won't give me the quest to unlock midas savage.

Make sure you really completed the questline from Midas normal. Check if there's an additional quest, should be outside in Dravanian Hinterlands, if you missed one.

oh im sorry. i've just checked and talk to the lightkix NPC. i noticed that i can't enter midas savage through DF?

No, Midas savage isn't in duty finder yet. You have to use Raid finder (in the main menu) to enter.
Once the next raid tier gets released it wll probably be put in duty finder too.