Ok, two different things going on here.
1) The only "Epilogue Saves" the game ever makes are after the Coronation (before the Epilogue, actually) in DAO, and at the very end of WH. In DAA and GoA the last auto-save is right before the Final Battle. All the important plot-flag decisions have been made by those points, (and there are no decisions in GoA that matter outisde of it anyway, although you may have leveled-up) so there is no "auto-save before the credits".
2) One cannot take a character "backward in time" between the various campaigns.
The canon time-line is the following: DAO -> DAA -> GoA -> WH.
So you can import a character from a save made in DAO into any of the later ones, but if you go DAO -> WH, you cannot import the Warden from the WH save back to any other campaign. Same for DAO -> GoA. You could continue with that character on to WH, but not back to DAA.