I you want just elites in a condensed area - then run Act 2, Vault of the Assassin in the Desolate Sands. Start the game in act 2, take WP to Black Canyon Mine, run the circle of that zone and get 1-3 stack. Then WP to Road to Alcarnus and run east, cross the bridge and that first zone should have a pack or two. Then WP to Desolate Sands and search for the Vault of the Assassin. Inside is a bazzillion packs and that's your best condensed area for champs/elites.
Once the Vault is clear, log out and restart and you will start in the Vault by the entrance. I go out (back to Desolate Sands) and then TP from there. That way, when I WP back to Desolate Sands, I know where the entrance is and run straight to the Vault.
Now. That's not the best area to farm Paragon exp. For that - Google the words "Alkazier" and "run". Feel free to improvise on the Alkazier run, because there are good variations to the theme.