I know we're only halfway into this season, but being stuck inside with no foreseeable future of being able to go outside, I might as well crunch the numbers and post before I forget.
One of my pet peeves for the past few seasons has been the gross underestimation of how fast the season start is, from the 1-70 process, to being able to get to T16. I browse the diablo forums, social media, etc., and often see people stating that an hour to two hours is normal, that they'll be playing T13 within 3 hours, etc. So, in Season 15, I started keeping track of stats at half hour intervals. As expected, what people say vs the reality are completely different.
Now, while I have stats going back to Season 15, since it's only been the last 3 seasons where you could cube a weapon too, I'll focus mainly on Season 20, going back to Season 18. Unfortunately, I wasn't able to get EU the past couple seasons due to work. In general, what I find is that Asia typically has the fastest overall start, followed by EU, and lastly Americas.
The 1-70 Race:
Let's look at the 90 min mark. Seasons 18 & 19 had 100+ players who hit 70. On EU, Season 18, 53 players hit level 70 within 90 minutes. On Americas, Season 18, 38 players hit 70 by the 90 minute mark, Season 19, 87 players hit level 70.
Now, onto Season 20. Prior seasons, there was an exploit that was used throughout the servers to reach level 70 quickly, so Asia and Americas plummeted. On Asia, Season 20, 24 players hit level 70 by 90 minutes, and on Americas, 65 players hit level 70 by the 90 minute mark. To be fair though, Asia did have some server issues on the day of season start, but not enough to warrant that big of a drop.
So, here's where the myth comes in. People tend to view the season start as a 1-70 race, when in reality, it's more of a 1-Chapter IV completion race. Let's look at 2 1/2 hours into the season start. In prior seasons, it would take roughly 3 1/2 hours for the first 1000 people to hit level 70, and this season, Americas was at 1000 by the 2 1/2 hour mark. On Asia, 587 people.
But, this becomes a little more interesting. On Asia, 12 people had placed on the GR Leaderboard compared to 7 on Americas. Five people on Americas had completed a GR 20 vs 6 on Asia. That means, at most, 2 1/2 hours into the season, fewer than 10 players could have possibly completed their Haedrig's Gift. Well, the Trag set is horrible, and necromancers would want to go after LoD, right? Fewer than 40 players were on any GR leaderboard on both Americas and Asia, and this includes groups also. This means that only 6% of players who were even 70, 2 1/2 hours into the season, could have possibly acquired an LoD gem, and fewer than 1% could have completed a set via Haedrig's Gift.
Around the 3 1/2 hour mark into the season, the top 100 players averaged roughly Paragon 75. Five hours into the season, they're almost all above Paragon 300.
Keeping a closer eye on things, the real slowdown of the season start is not the 1-70 race, it's the completion of Haedrig's Gift. It's taking the top players roughly 1h45m to 2h to complete the first 4 chapters, and these are players who are hitting 70 in under 90 minutes, some even as low as an hour. It's taking longer to get the gifts, starting at level 70, than it is to level up their player to level 70. This can allow enterprising players, who are willing to slow down their race to 70, to actually speed beyond those top players.
Now, below are just suggestions, I'm sure there are more optimal ways.
One huge thing is to build the chapters into your 1-70 build. Killing bosses aren't going to be as fast as pure leveling, but post 70, the experience is less of a factor than getting the gear. And if you're going to get experience anyway, might as well build it into the leveling process. All of Chapter 1 can be done once you're level 60. And most of Chapter 2 can be completed (the only thing you can't do for Chapter 2 is reach level 70). So, when you're running your levels, and finished a rift, or need to restart, check to see if you have a Chapter 1 or 2 boss as a bounty, and if so, dump the difficulty and get those out of the way. Make sure it's a bounty though, so you can get a little extra experience. And make sure you hit level 70 on an Expert Rift or above, if you haven't already done that. You can start the rift at any level, but you'll be after a Greater Rift stone, and as long as you hit level 70 before you hit the boss, you should be good.
Now, what seems to really be killing people are the bounties. In prior seasons, I would have suggested to start the bounties when you're close to 70, but I'm going to amend my thinking. The prior logic had always been, doing bounties for leveling is bad. But looking at the total time to Chapter IV completion, I'm going to disagree. It's slower to 70, but you're still gaining XP. You'll still need the 5 jewel crafting recipes though. The vendor in Chapter 2 sells 3 jewelcrafting recipes, one for 2 million gold, two for 5 million each. Later on, with a gold goblin or a vault, those should be within reason for purchsing. So, don't do all the bounties. This will differ between solo and group.
I'm not quite sure when to do these yet. My current line of thinking is perhaps when you're able to use your level reduce weapon, preferably below level 50. We're going to do Acts 2, 3, and 5, which are the slowest acts. Get the bosses out of the way first, as you'll want to be at your most powerful, so you won't need to dump difficulty later.
One player will sacrifice their time to do Acts 2, 3, and 5 by themselves, while the others level up as normal. While they'll be tons of levels behind, when they rejoin, by the time you hit 70, they'll only be a few levels behind, but still able to contribute to the Chapter progress. And, since they're not level 70 yet, they can't completely Chapters 2-4 yet anyway, but once they reach 70, they'll get their rewards along with everyone else.
When you hit 70, you'll focus mainly on Chapters 1 & 4, which are the fastest bounties, to get the rest of the jewelcrafting designs.
Legacy of Dreams:
This will actually make everything easier. Don't worry about trying to do a T4 rift, or even a T1 rift yet. Your goal is to get LoD asap. A normal rift and a T1 rift both open up GR13, so run the highest you can while still being able to one shot stuff for speed. And dump the difficulty to normal to get Malthael out of the way for Reaper's Wraps. And you have a Sage item you can craft. So, at minimum, you should have 3 legendaries for LoD by the completion of Chapter 2 left. Now, complete a T4 rift and either complete the GR20 and then the rest of the chapter, or the rest of the chapter first, depending on how low of a rank you want. Regardless, you should be completing your set 20-30 minutes faster than the traditional way of leveling to 70, and then running Chapters I-IV.