Warbringers drop 3 rep tokens and a small bag, with a chance for a bigger bag (and mount of course). Scouts drop one token, with a chance for small bags and a smaller chance for big bags. It takes me 2 minutes to kill a scout, and 8 minutes to kill a warbringer, so I'd say it's about similarly efficient in terms of loot/time.
If you can solo warbringers, great, otherwise, scouts are equally lucrative.