In my opinion 3 slots are fine, even though all the other "elite" weapons are 4 slotted. Do keep in mind that Taekwon normally don't even have an weapon, as long as the weapon does not get less than 3 slots and makes up for the atk boost you get with Running , then I'm fine with it.
However...
I thought I already explained why you do not see that many rankers at this time. And that is also why I think the list should get longer to at least 15 slots. It would certainly not kill the competition, but it would give some more people the chance to become an ranker, and seeing some people that are below 60 points gives more people courage to try and get in the list as well. Right now they see that the lowest person has 59 points, meaning you have to get 60 points to get in the list. Most people don't even try to get into the list because of this. ..
I personally am also busy making an Taekwon Ranker, but when this person offered me to make one with him the first thing I said was : Hell no. Because the ranking list is short and has so many points even on the 10'th spot. it discourages many people but right now it's more of an goal to me to get there, even though it will take a while because many of the monsters don't work with taekwon mission.