Right now I would say for this team it is best to invest in the offensive line and see how Tannehill does in 2018. If they get a top pick and a QB prospect that they like is available then go for it. However a rookie QB behind this garbage offensive line is going to take a beating and possibly lose confidence. So I say put together an above average offensive line and continue to improve the defense.
That's where I'm leaning as well. Look at Dallas. Drafting Elliott and Prescott in the same year made a huge difference for that franchise. But, they may have not been a factor if the Cowboys hadn't built the offensive line first.
It's like building the house without the foundation.