Your crafting guide should talk more about snofleur. As others have pointed out, it's easy, fast, and safe in the exalted plains. Not only is it the easiest tier 3 leather, it's the easiest tier 3 resource. This will be important. Farming metal in the Emprise takes forever until you gain some levels. I'm pretty sure that your level affects the amount of metal that drops from each rock, and if you have to sneak around the enemies it takes forever. Here's the big deal I think you need to add
--Buy the sturdy hunter coat from Val Royeaux as early as possible. Immediately after you get Skyhold, you can go to the Plains and craft a snofleur coat for your rogue. It will be way better than anything else that will have dropped. I think it has more armor than a paragon luster sturdy vanguard, although I may misremember. It's a godsend for dagger rogues.
--If you have the patience, keep farming snofleur. Snofleur leather removes class restrictions. You can outfit your entire party in snofleur and coast through melee enemies for a while. I usually wouldn't bother though, because
--the first tier 3 area you want to unlock is The Hissing Wastes. I would do this before the Emprise. Even if the enemies are too strong for you, you can usually sneak past them and get the camp by the canyon. In the canyon is a merchant who sells tier 3 armor schematics. They're incredibly expensive, but save up all your money for the sturdy prowler, and get the prowler mods when you can. Don't get the dalish scout because I think it has race restrictions, and because it's unmoddable, it's not as amazing as it looks.
--Now you never have to buy a mage schematic again. Put all your mages in snofleur. It's got more armor than robes, and it allows you to stack crit chance and ranged defense instead of attack and magic defense. If you have flashpoint, and especially if you have an artificer, then crit chance will do more for your mage damage than attack will. (Possible exception for Dorian) I also find ranged defense more useful than magic defense for general adventuring. The biggest downsides to leather are reduced opportunity to stack spirit resist, and the fact that the leather outfits for mages look really stupid.
--Unfortunately, although snofleur is a really easy way to get huge armor ratings early, it has no good stats for non-rogues. In fact, there are only a handful of tier 3 leathers that actually have the stats non-rogues want. This most time-consuming part of this will be getting the utility and attack leathers you need. Dexterity is completely useless, flank damage is mostly useless, and crit damage is disappointing. You really want cunning in utility and crit chance in offense. Your only real options for cunning is lurker scales. They roam around near the north camp in the hissing wastes. You have to sneak past some dangerous rifts and venatori to get there, but the lurkers themselves are weak and drop large amounts. Great Bear is pretty much your only option for crit chance, but they are incredibly rare spawns in the graves and I've never seen one in the Emprise. One of them should drop enough for one set, but farming great bear for your whole team is a nightmare. You probably have to wait until you take the Emprise and use the "gather leather" operation to stack it up. Consider forging a bad version while you wait
--While you save up or wait to find a tier 3 metal schematic, you can put prowler gear on your warriors. It will be better than tier 2 metal. Once you do get a metal armor, it's actually an interesting choice. Keeping your warrior in leather is not a terrible idea if you want to deal damage.
--TLDR: Reach Skyhold, immediately open Exalted Plains and farm Snowfleur. Craft hunter armor for everyone. Unlock Hissing Wastes, dodge enemies to reach canyon. Buy prowler armor. Craft prowler armor for everyone. Get lurker scales from north wastes and great bear from "gather leather" operation with Leliana, once you take the keep in Emprise. Stack +Cunning and +Crit Chance on your mages and warriors. Optionally replace prowler gear with battlemaster on your warriors later.