I not only think its a waste of time for grads, but a waste of time for the arena team and the lower years. A dueling challenge can easily last 1 - 2 hours depending on how many people join. And you don't even get a reward for 5th place in a class with 60 players. Also players who join the server for the first time see a class and don't even know that's the case and that they'll get 1 shot by someone whos 3 years above of them. I don't think its necessarily "fun" when you spend about 30 minutes dueling people who are about your level just to be 1 shot and given no prize.
You can still have these connections with players outside of dueling challenges. It doesn't depend on them being allowed into dueling challenges. Dueling challenges are structured so that the the best players always win. And those players won't be able to even reach near the top in a populated class. Dueling classes are still a thing, and they're pretty much as balanced as you could want them to be. And they are almost as frequent, if not more than dueling challenges.
Like what I said above, its a waste of time for the arena team as well. Challenges are a time investment for everyone currently, especially the arena team. They have to record and track the placements of everyone dueling and it takes a long time. I barely see any lower years participate in dueling tournaments. Last time I did the opposing team (all grads) let them win the first two (took a while for them to kill them) then just obliterated them the 3 rounds after. I can tell you it wasn't much fun for the 10 people waiting to duel. The argument that they get help for future tournaments is flawed. The amount of time it takes to level up and get gear isn't fast whatsoever. When those lower years level up and get decent gear they have more than enough time to attend those dueling challenges with gear and see what its like to be in a tournament.
The amount of grads without gear decreases as time goes on. When it was the first month, yeah I could see that being a problem. But now its just a handful of people. Having a year requirement definitely would make a difference. It's also easier to check than health because its just one command away. Also the arena team doesn't have to check every single person to join a class. They could just ask in chat for all the lower year to leave. And the ones that don't would probably be known to the arena team because PW has a pretty small community you pretty much know who is a higher year than others.
Maybe in the future gear won't matter than much. That doesn't mean we can't have this regulation. Just like how dueling classes were mostly FFAs before Revelius. Then they changed to year FFAs. It doesn't take a whole system rework to add this or remove it.