If you get fade touched cloth, some of it has 10% chance per hit to proc hidden blades, with the tier of cloth adding hits(3 for tier 1 and up to 5hits hidden blades for tier3). Type of cloth is the shit that's most often dropped too, at least for tier2, I think I had 5 of the fadetouched ones. Annoying to farm though.
Prowler mobs are annoying but are fairly rare. What I did was just follow them so you have them on the targetting thing and spam "attack my target" so your mages pop it out of stealth, then fuck it up. With tempest you just pop lightning flask at the start and kill them, assuming there's only one, that works too.
Tier3 schematics OR tier3 metal breaks the game very early if you rush for them, both break it even further. For metal there's a few ways, like unlocking a high lvl zone as soon as you get to skyhold(iirc you get access to them, they just cost like 20-30power) and mining easy metal(Hissing Wastes itself has a ton of shit early on) or capturing western approach keep right away so you can get everite from missions(but that's longer tbh). Hell you can get tier3 metal in Crestwood in the cave dungeon thing, Stormheart spawns in there, it's a bit slow to farm since you only loot them 1 by 1 at that level but you only need like 8 or some crap per weapon and it's very fast to reset since it's a small dungeon, and they'll be like 200+DPS daggers with the tier2 schematics, which is like double what you're expected to have at that point of the game. They really didn't think this shit through much at all.