The secondary isn't great, but with our system it doesn't need to be, and it's probably not something we'd spend a top pick on anyway. Adding Gaines helps our secondary if he can get a pass rush.
Offensive line is definitely the biggest issue going forward. The hope is probably that Pace has another year in him. If not, Chris Williams goes to LT and Kevin Schafer starts. Not ideal, but passable I think.
On top of all of that, the biggest situation is if O-Gun leaves and we have nobody to take his spot. You can't run this defense without a good pass rush.