This list is for standalone, legacy Dragon Age: Inquisition, so it only lists the best gear that is available before any DLC/extra game content.
For archer rogues, the best weapon is the Masterwork Spiked Longbow, crafted via schematic. This bow has a base DPS of 172 if you use a Tier 4 crafting material like Dragon Bone. And that’s not even including the offense and utility slots, the Masterwork material, and the Rune and bow Grip that you can attach later.
Schematic Location: Found in the Tomb right next to the Sand Crags camp in The Hissing Wastes.
I would also recommend that you pick up the unique Longbow of the Griffon from the Temple of Mythal (you can find it after doing the puzzles in the Temple and then talking to the Elves). This bow has a special effect which fires 3 arrows at a time, which is only useful against a large enemy like dragons. So you can switch to this bow whenever you’re fighting dragons.
For dual-wield rogues, the best weapon is the Masterwork Dual Curved Blade. Craft two of these with some powerful masterworks like Fade-Touched Plush Fustian Velvet, and you’ve got yourself some serious damage.
Schematic Location: This schematic is found in the Burial Grounds Tomb in southern Hissing Wastes.
For mages, the Masterwork Archon Staff schematic looks good at first, but it wastes stats on a metal utility slot. The best weapon is then a tie between the Seer Staff and the Masterwork Mortalitasi Staff.
The Seer staff has more offense slots which are slightly better than Utility slots for pure damage, but the Mortalitasi staff has a slightly more powerful Utility slot with 8 cloth used instead of 6, so in the end they are near equal.
Schematic Location: Both schematics are random drops, although the Mortalitasi staff is definitely a lot more rare.
the best 2-hander in DA: I is the Hossberg Twainer. Although it has the same DPS as several other crafted 2 handed weapons, it has 3 offense slots which makes it the best option. You can stack 3 + % attack materials in the offense slots, giving you the highest possible damage.
Schematic Location: The Hossberg Twainer can be bought from the merchant in Suledin Keep.
The Sulevin Blade unique two-handed sword is a good alternative, but if you use the best crafting materials and stack the + attack stat, the Hossberg is still ahead damage-wise.
For tank warriors that use 1-handers, there are 3 crafted weapon choices: Serpent’s Rage, Griffon Mace, and the Masterwork Tevinter Longsword. They all have the same stats, but I would recommend using the Griffon Mace over the other 2 because it has 2 utility slots instead of 2 offense slots, which will give you slightly better tanking stats instead of damage stats.
Schematic Location: The Griffon Mace schematic can be purchased from the merchant in Suledin Keep, but only if you have the Short List Perk from the “Connections” Perk tab. Serpent’s Rage is found in the Tomb northeast of the Statue Camp in The Hissing Wastes. The Longsword is a random drop (and is very difficult to find, judging from what people are saying on Bioware’s forums).
The Masterwork Sentinel Shield is not that great because it has a utility and an offense slot, neither of which are that great for a tank. Ideally, you want to have a shield with two defense slots so that you can stack up mitigation (magic resistance, melee defense, etc).
This leaves us with 4 choices: Polished Shield, Noble Shield, Formation Shield, and Dwarven Proving Shield. All 4 of these shields have 2 Defense slots, but they vary in the type of material used in these slots.
Generally speaking though, they are about comparable and will give you slightly different kinds of defenses.
Schematic Location: The Dwarven Proving and Formation Shields are sold by the merchant in Suledin Keep. I think that both the Polished and Noble Shields are random drops, seeing how I couldn’t find a location for them anywhere.