Yes, not meaning 4-5 mids from our best-22 is a very important clarification, and the other questions are moot if you didn't mean that.
So best-22-wise then, you think just one player for next year (Jobe replacement/improvement) would put our midfield up there with the best (barring injuries)? If so, I'd agree. Assuming that McGrath will also probably be spending more time there next year too.
But I would also then think it'd be worth giving up some early draft picks if we could get someone like that, rather than using them on youngsters who would likely need a few years to develop. Hooker, Hurley etc deserve it. Winning the premiership next year, after whatever happens this year, should now be the focus. Preference though would be to get someone through free agency (having some young stars developed in a few years to win then as well would be great). Rockliff would be perfect.
Depth considerations should just be given to later draft picks/pre-season draft, and banking on improvement from at least a couple of the ifs.