The only thing about Mayo, Spikes, and Hightower is they are mainly run stoppers with limited to poor coverage skills. Yes they are 3 very talented LB's but we are in need of a linebacker who can come in on 3rd down and run with top TE's and not get burnt.
Hightower actually has good range to make tackles and can pass rush a little, but not very good in coverage.
Mayo has great tackling range and is decent in coverage.
Tavon Wilson is supposed to be the kind of dime back that can cover TEs on third downs.