Since the v1.10 patch reworked the experience rewards and high level penalties, leveling a character to 99 has become a significantly more time-consuming endeavor. Up to 85 or even 90 isn't that slow, but once you get past 91 or 92, the leveling speed begins to deteriorate dramatically. Once you get past level 93, only three bosses are of a high enough level that the player does not receive an additional experience penalty. Baal, Diablo, and Nihlathak are the three demons. Recently, numbers and experiments have shown that solo Baal runs (trips down through the Worldstone Keep, followed by a long battle to clear out Baal's Throneroom, and then killing Baal himself in the Worldstone Chamber) can be just as effective over time as solo Nihlathak and D2R Items Xbox Series runs. In order to be taken seriously, serious ladder teams usually have their primary character kill Baal and D2R Items Xbox One on each run.
The following figures depict the number of Baal runs required for each level up, as well as the total number of Baal runs required for the journey from level 90 to 99. This assumes that a player kills almost nothing on Worldstone Keep levels 2 and 3, then kills all five packs of Baal's Minions on /players 8, before killing Baal himself on /players 3 and higher levels of difficulty. The experience value of Baal does not increase after three players because of a bug in v1.10 and later versions.
On Battle. net or in multiplayer games, players who complete these runs will typically have to kill a few more monsters on their way down to the Throneroom, but the experience gained from doing so is insignificant when compared to the total number of monsters required.
When played by talented players with powerful characters, Baal runs can be zipped through with incredible speed and efficiency. Runs can be completed in under 2:30 minutes, including the time it takes to create the game and get to the starting point in town. That's a total of two minutes, thirty seconds.
Baal is in charge of the figures.
This chart depicts the number of Baal runs required for each level up, as well as the total number of Baal runs required to progress from 90 to 99. It is important to note that nearly two-thirds of the total runs are required to move from 98 to 99. One who plays extremely quickly, particularly one who receives turbo assistance from friends, could theoretically spend more total play time going from 98 to 99 than they did going from 1-98. There's an interesting balance that the D2 patch designers have achieved there.