Who should be responsible? IT or Instructors?

I'd say that IT folks should concentrate on the tasks that require their special technical skills, such as keeping the network running and cybersecurity. They aren't trained in adult-learning theories or instructional design, so they shouldn't do that. 

Yes, it takes some practice to get good at Storyline. Rise is a lot easier, so your team could consider using that, instead (though you'd have to give up some functionality that's only available in Storyline). 

Another option would be to hire someone just to develop the courses. Depending on the volume of courses, that might be a full-time position, or it could be done on a contract basis.