You're talking like that dice-system would be somewhat like "epic" or whatever they call "massively enjoyable by nature" in the internet. This only goes as far as your imagination, but I'm telling you that anyone could imagine anything if they wanted to. That is not an argument that strengthens the genre. "Sandbox" game is nothing but a false calculation and a very cheap way of stating that you're unable to implement worthwhile elements as a developer. On top of that, the least people are actually still taking imagination as their main reason of playing MMOs (real RPers that follow an actual fictional social system, in other words, reasonable rules).
Also, more of the upcoming new titels are going the way I am suggesting and thinking about for years than ever (just check the TERA Online and read
this article). This just proves that their market research isn't going the same linear way as it used to and that means that many people must have realized the same thing I did. You can even find those people in this forums. Dice-system MMOs were an abstractive fluke after Ultima Online set the pace and some others just used the simple way of monotony = dopamine factor by adding it to their own products.
All of this is way cheaper than you think it is.
And dude, isn't it reasonable that people want what they're addicted to? I just don't think that this counts as legit pro argument.