Make Leo missions actually work. They're the gateway into PvP.
Right now, it takes an immense amount of effort and coordination to make a Leo mission actually happen, at least on standard, and at least for the party ones. First, it takes 1-2 hours to get 6 or 12 people spread across two parties. Then, you need to get everyone into the same town instance. Then you need both groups to enqueue themselves. Then for some unknown reason you have to stare at the screen for a minute even though the leaders of both groups are sure they've done everything right. Throughout this whole process, there's little transparency into how long waits are, what tweaks need to happen to get people matched, etc. Then, once a mission actually does start, it's very common for one or more people to get booted out for no reason. This can happen if they mistakenly touch a portal (which unfortunately appears in exactly the same place as the flag so it's easy to misclick when trying to rescue a mission). Other times, nobody knows why someone got kicked out of the arena. I still have no idea how to get back in after being sent back to town. Basically, the mechanics are frustrating to the point of being broken.
The other frustration with Leo missions comes from a single non-cooperative user. Some people are geared to where they simply cannot be killed, even by another equal tank. If they come into a mission, they will often prevent quick wins by trying to rack up kills. This becomes very frustrating for teams that want to coordinate to make sure all 12 people that just spent 2 hours staring at their screen can actually get Leo credit. The longer a mission goes on, the more chance that there will be technical glitches, meaning that even if a person's team wins, they may still not get credit if they were somehow kicked out of the arena.