At the time of me writing this, the compensation DMT is ongoing, and, well... once again it is lagging just like last time. It's even acknowledged by Ghiblee on Discord.
I'm not a professional programmer or anything, nor do I know anything about MapleStory's code, but as someone with a bit of experience, a certain possibility did cross my head:
I'm assuming the lag between cube usage is caused by tons of people doing the exact same thing: Re-rolling their potential stats. I think it's done by sending a re-roll request to the server, and then the server responds with the RNG'd new stats.
When the server has to receive requests and respond a trillion times a second, it's obviously gonna cause strain and lag.
IF what I said is correct at all, then how about this - Make the reroll for Black Cubes client-sided.
I.E when using a Black Cube, don't send any request to the server. Instead, show us the new RNG'd stats in an offline/client-sided manner, AND increment the number of cubing attempts we did.
Send a request to the server to update our equip's potential ONLY after we click on one of the choices (The 'before' or the 'after'). Update the number of cubes in our inventory accordingly as well.
My suggestion doesn't account for Red Cubes, but a lot of people use mostly Black Cubes during DMT (I think lol). So this should reduce the number of requests the server has to receive and respond to, thus reducing the lag.
Again, I'm not a professional nor do I know the behind-the-scenes of MapleStory's code, so my suggestion could be flawed if my base is incorrect. But hey, wouldn't hurt to try
Maybe someone can suggest improvements to my suggestion, or give a different perspective.
Happy DMT lul