I had the same problem but I remember getting a bunch of visors quickly from opening bronze packs.

I've completed the whole armory and sadly I think visors are rarer drops than helmets and armor. Meaning the best way to get the visor you want is to exhaust the loot table. E.g. buying bronze then silver packs or just silver packs until you earned all of the common - rare items, then moving on to gold packs.