You'll want as slow of a weapon as possible to max out Seal of Command damage. You want your weapon speed to be in the mid-high 30s, 3.2 being the absolute fastest you'll want to go for your level (as you get higher you'll want to get at least a 3.6 weapon for the most part). If you are alliance, you should do your
Verigan's Fist quest ASAP, as that will help you out a lot. (I'm assuming you are at or around 21 since the weapon you posted was 21). If you are Horde, the
Sin'dorei Warblade you can get from the Tranquillien quests will be the best weapon you can get (even slightly better than the Paladin weapon, the
Blood-Tempered Ranseur) because of the extra Seal of Command damage.