My suggestion was assuming most players would only use the drop for arcane pieces, since they're extremely hard to replace. Every other equip should be able to be upped to at least 20* without the use of these items. With the current BIS knowledge i have, players would be getting 4 arcane equips excluding the Will patch, and 17 - 22* is basically a slightly harder version of 7 - 12* for tyrants, and because of this, I would say 15 a month would give a comfortable method of progression.
From what I've seen since I've been back, there are players who are on the brink of reaching these end game content, but just have not gotten around to forming squads yet. This would give them a great incentive to do so, not to mention players would automatically get loads more range from upgrading their currently 15* gollux and CRA gear to 20* as previously mentioned.
Again, I'm not looking for new content which would be cleared within the next 3 months by 30% of the server. That'd be such a wasted opportunity, and I would hate to see us go down that road yet again.
Edit: Just realised Poro missed an important detail. There's more than 1 end game boss in the game
In my post i mentioned 3, on top of changing Hekaton shop. That means end game players are getting more than just 15 a month. Also, I did mean to talk about shared party drops in my post, but it somehow slipped my mind, thanks for that!