Honestly, the biggest issue with Mahjong on the NA servers is that almost no one plays it. I largely feel like most people drop mahjong pretty quick because the rules are hard to understand for a beginner. And only those who truly want to learn keep playing after the first few games. So, how can you incentivize players to keep playing and learn and get better? I think the simple answer is MGP.
It's in the golden saucer, and aside from a weekly challenge log that everyone does on Tuesdays / Wednesdays, you get no MGP at all for playing. It doesn't even have to be a large amount, just anything is better than nothing.
I personally suggest that you also make it a scaling reward of MGP based on where you place. 1st place could be 1000 MGP for an full match and 500 for quick match, 2nd place 500 for full match, 250 for quick match, 3rd place 300 full match, 150 quick match, and 4th could be 200 full match, 100 quick match.
That's a grand total of 2000 MGP handed out to players for a game that will around 40 minutes. 1000 for something around 20-30 minutes. That way, it's not the best way to get MGP by any means, but at the same time there is SOME incentive to play outside of just having fun with it.
I wouldn't make this thread unless it was possible to even queue properly. The longest I've waited for a novice quick match game is over 50 minutes. And, even if I do get into games quickly at times, it's usually with the same three-six people over and over. It's really frustrating to see the same people and never a change of pace at all in people's strats etc. by running into more people. You do occasionally also get the new player, but because most of the matches are quick matches, they usually play really small hands and end the game before you can really do anything, even if it means they'll lose in 4th place.
Point is, the healthiest thing I can think of for Mahjong in XIV is to add incentive so more people play it.