I don't know. The fact is that LoL has a huge playerbase, meaning that top players plays versus equally skilled player no? (Never played it, so I really have no idea how matchmaking and ranking work). So yeah it's seems fair to say that you have something close of a 50% win rate.
ffxiv doesn't have this huge player base meaning that you kinda play with what is avalable. It's not really pitting you against equal value players, it's just that the queue is a flip a coin factor so you have a 50% win. Then if you re unlucky enough you get increadible losing strike where you can't do nothing against even if you re good.
Don't get it wrong, I know that it is the same issue everywhere. But I don't feel at all that a 50% win rate here show that you have foes with equal strenght but more that you have half of the time the weakest link due to the not that high number of people playing.
And consider too that they changed the way you lose point. Before a 51% win rate allowed you to progress. Now, at least for what I saw in bronze you have a -15/+25 meaning that you need a 41% win rate to progress. Which probably show that it was way too hard and frustrating to progress because you needed this 51%.