I posted this in another thread but thought it might get more visibility with it's own thread.
Perhaps the Otto's box could cover a DIFFERENT part of the level range that Bigby's box applies to?
Bigby's box to go from 7-15, and Otto's box to go from 15-20.
Level 15 to Level 20 is currently 850,000 XP for a first-lifer. The Otto's box currently gives 930,000 xp on a first-life character but the amount of XP needed to get to 20 is going to increase. So, the amount for a second and third life is going to increase even more. At least this way, any extra experience from XP stones could be split between Epic Levels and EDs evenly.
More importantly, if they make the Otto's box grant a very similar amount of experience as it used to, but slightly more, no one will feel like it is a huge nerf. Both stones of experience could coexist and when used together could put you right back into Epic content!
Also, a bundled pricing for both stones of experience in a single box might make the total TP cost cheaper than buying XP pots to level from 15-20 when all things are considered. The Bigby's Stone would truly be "Handy", in leveling quicker, but Otto's stones would still be "Irresistible" for those that want nothing more than to get straight back to Epic questing.
I could even see niche for adding a Mordenkainen's Magnificent Box for 2995 TP.
My suggested contents would be:
3 Mordenkainen's XP stones for leveling 1-7
3 Siberys Spirit Cakes
50 Gold Seal Elixirs of Greater Healing
25 Major Crafting Experience Elixir (get it, Mordenkainen's Disjunction?)
25 Remote Item Deconstruction
The great thing about having multiple boxes is that it breaks up the level range into several different groups of people that either will/will not purchase a box for that level range. It also discourages people from buying every box available as it gets more expensive the more you get! Not everyone is going to want to spend 12,000 TP to skip all the content, but someone with multiple alts that they just TR'ed might really be interested in a Mordenkainen's box.
Just my 2 cp.