Well that really depends... for an army of alts... or just logging in each day to spend 15 minutes collecting the stuff, it does add up over time. And that's the heart of the issue: The garrison provided so much at such a low investment of time, folks would just log in to do their "daily chores" instead of engaging with other players in content.
And that's a benefit of M+, bringing some group content that players can engage in even during periods of expansion lull.