At Your Command

The outpost structure you choose is personal - the choice partially depends upon whether you would like to use [spell=164399] or [spell=161768] while you are in Talador, and partially depends on which follower you wish to gain. The guide at http://www.wowhead.com/news=242853/garrison-outpost-guide-zone-wide-perks-quests-followers lists the different quests that you will take, and reveals the different followers you will get, depending upon which spells (i.e. outpost structure) you choose. The followers awarded at the ends of the quest chains are [follower=154] (with [garrisonability=171]) if you choose Arcane Sanctum, or [follower=155] (with [garrisonability=6]) if you choose Arsenal.

I chose Arcane Sanctum because I don't like the artillery tactics in WOW. OTOH, you might like artillery. Or you may want to make a choice based upon follower, but I cannot predict which follower will be more useful.

Did this on my alliance character whilst I was leveling and now I've faction changed, it's asking for me to do it again, Problem is, I already have the building in place! Anyone have this problem?

http://www.wowhead.com/spell=164399 Destroys most elites. You get 3 charges of it and it does all of its damage in a couple seconds. I think it works best for soloing rares and other elites.