Under Bruce we turned the previously maligned McShane into a reliable option, we had a rotating list of keepers with Amos, Jak and Stockdale between the sticks, we had the skeptical signing of his son coming in at CB, and battlers like Evans, Hobbs, Rosenior, Meyler, and Dudgeon who all played significant roles. All players who improved and proved that they could step up to compete for automatic promotion and then a number of whom played a role in the PL.
But Dudgeon and Rosenior were in a completely different league to Elder and Coyle.
Even when Evans, Hobbs, Rosenior and Meyler all left, they all went to Championship clubs, Elder and Coyle will be heading back to L1 so I don't really see your point.
I'd take Evans, Hobbs, Rosenior, Meyler and Dudgeon in a heartbeat, they'd improve us immensely.