Couple of quick points on 5 mans in Garrison, 2 things I do which helps ever so slightly.

Firstly, when questing in the starting area (Shadowmoon valley) there are a number or quests that come from the Garrison and require handing in back there too. Once all toons have handed in, get each toon to right click their portrait and "visit leaders garrison" this then gets them all together outside the front of the Garriosn phased together and saves having to run them all out separately.

Secondly, if you use Jamba make sure when flying anywhere to have flight window open on all screens and "taxi" still works sending all toons to the same flight point, even if in their own Garrison.

Neither of the above will save you 100's of hours but make life a tiny bit easier.

Jim.