I believe FFXIV artists could do a much better job at drawing/rendering a DRK with a Scythe.
Actually some Chinese used to use Scythe like weapons (including a a blade placed/curved along the haft) until they combined it with the Spear to create the "Ji" (Chinese Halberd) which was superior to both the Scythe and the Spear. If you want to argue that a weapon shouldn't be used in a fictional game (where practicality doesn't hold any weight over appeal) despite having skill to wield a weapon effectively over the potential of a weapon itself then technically a DRG should try to focus only on halberds since the spear and lance are inferior as well.
I'll admit FFXI made some terrible decisions, but there are also a LOT of good decision that were made in the development of the game. Despite facing the anomaly that is WoW even during it's prime, FFXI is still a subscription based model after 11 years of success. To show that the game was a success you can quite easily look at what I have come to understand are ALL modern MMOs (including but not limited to severely hyped and highly anticipated games like Rift, SWTOR, and Guildwars 2) going Free to Play after only a matter of months from launch.
I wouldn't say FFXI's DRK (or any melee based job due to severe lack of actions) was a great decision for FFXI, but I do feel like wielding a Greatsword or Scythe was a good choice. Personally I'd prefer to see DRK wield Greatsword as the wpn of choice, but I'd still prefer a Scythe to a 1H w/ or w/o a shield and whether the DRK is set as a DPS or a Tank. Greatsword emphasized with Parry and being able to cross-class with DRG would be pretty cool.
Necromancer would be pretty cool with a Scythe, but as with SMN holding a book I feel it won't be quite as symbolic as intended. After all we only use 2 pages in our book (as clearly demonstrated with the Titan book with 2 stone slabs), the rest is just paper weight (lawl). Quite useful for smacking mobs. At melee range a good SMN can actually spam Ruin II and get 1 auto attack in per cast as opposed to spamming Ruin and getting 1 auto attack in per 5 casts. Somewhere around +25 DPS IIRC.
Also a Katana is swung from side to side (or any weapon really). You can angle the strike in any direction, but when you do you only attack in one direction. The major differences between weapons are the transitions between each attack, the damage type (IE Slashing or Blunt), and the range. Also a Scythe can be used for blunt attacks (which would be more prominent compared to other wpns due to transitions between attacks) with both the head and pommel, as with any non-piercing wpn.