Unique equipment is nowhere near t3 crafting, not even close. You haven't seen what you can do with crafting if you say this. Apart from some specific sitiuational OP uniques like bow of the griffin.
Also you killed lvl 14 dragon at lvl 19 fast. Is this a big surprise? You shouldn't even get XP for this fight
. Rogues have the best scaling with gear, so lategame they dish out a lot of damage, the broken level of damage is reached mainly through crafting though. Rogues being inferior to mages holds true imo for earlier stages of the game where you don't yet have the damage to take out everything instantly and need survivability/cc, at least in party context (solo archer rogue is one of the easier options pre skyhold). Lategame is broken anyway, I haven't had difficulty with a single fight past skyhold.
Late game Unique weapons can rival crafted ones, not surpass. Other than the Longbow of the Griffon, there are the Suvelin Blade, Certainty, Yavanalis, Song of the Marshes, Walking Death and Axe of the Dragon Hunter, maybe some others that I have never found (like the Perseverance Bow). I am pretty sure any of those weapons can serve the player just fine, capable of making the game quite easy towards the end.
Armors aren't at the same level. Except for the ones you get by killing the later dragons, the rest is lackluster in all aspects, especially cosmetic. But still, they shouldn't stop anyone from beating the game.
Now I didn't realize that Dragon's level has so low... that is embarrassing. 