Unless one is super competetive, I don’t see why one shouldn’t use the CR cache. Once one hits level 18 and can unlock the level requirement removal node, those mats can provide several level 70 items.
My recommendation is the opposite: just use the cache and get the next week one for the Altar.
That’s where the Visions come in.
I made a sample demonstration on the PTR, leveling 1-70, with no cache, in about 42 minutes.
Diablo 3: Season 30 PTR Necro No Cache 1-70 in under 42 minutes - YouTube
Yes, this is the PTR, so add time, but we’re talking an extra half an hour in live. This isn’t Season 28 where you’d be lucky just to have the weapon. Sub 2 hours without the use of the cache should be possible for most classes in an actual season, which is faster than most people have leveled traditionally.
Now, if you’re just after the smoothest 1-70 possible, sure, use the cache. Or, if you’re after the conquest leaderboards, use the cache. But if you’re just after blasting opening weekend, saving the cache will barely affect your leveling.
What would be really nice is if they doubled the challenge cache so we would have 1 to use and one for altar. I know it won’t happen but that would be the dream option.
Eh, being forced into the choice of quick lvl 70 or using it to unlock the Altar later is fine… The choice of one path or the other. The game has been accelerated to transwarp progression speeds enough already over the years, no need to push it further.
Besides, the Enmity portals provide an early source of DB, so faster progression without the CR cache is already possible. Just gotta get that gold to upgrade Haedrig and the mats to get enough chances to roll up to -30 level requirement on a L70 weapon.
Well, you don’t really need that as you can unlock the no level req without the cache.
If that’s the altar path chosen, sure.
There’s really no reason to go another way.
For the ones that know the path, I agree.
This is not correct. You can unlock the no level requirement without the cache, as others have outlined.
Yes, the seal you can unlock, but you don’t have the mats to take advantage of it to full effect, as in craft a full set of 70 items.
You don’t need the full set. Having just a level 70 weapon makes you fly to level 70.
Difference between a full setup and just a weapon is still entirely noticeable, so yeah, I would say my initial statement is entirely factual.
For those who take their time and don’t mind taking several days to unlock the Altar, what you suggest is fine indeed. But most people in my clan are like me and want to do it asap (by Saturday, or Sunday at the latest).
If you use the CR cache, you can still unlock 14 out 26 nodes within the first weekend. With little planning you can unlock all most important nodes. I’d prioritize QoL stuff over simple power.
Whatever ones chooses to do, there is no “one correct way”. Which ever way you do things is the correct way for you.
The second node unlocked removes all level requirements. So, you just need a diamond. Sand salvaging Soul Shards provides 90k for the 3 Imperial Gems, or 900k if you get a Flawless Royal. You only need 311k to upgrade the Blacksmith fully.
Now, this comes down to when the next season starts.
The route I took in the PTR:
Level a Necro to 18, as they can level faster than any other class. At this point, just face boss bounties, as at 18, you can get diamonds. 2 of these to craft a flawless diamond to upgrade the second altar node. At this point, you just need a Death’s Breath and gold. So, you have to find a vision, and preferably a floor with blue elites. Now, to be fair, it does seem like they nerfed the DB drop rate along with the Greater Rift Key drop rate, but you should be able to find at least one in a Vision.
As for the gold, keep fighting bosses. You can either face them on Normal, which will require multiple runs to get the necessary Soul Shards. On Normal Difficulty, the drop rate is roughly a 33% chance. This will take on average 12 runs to get the necessary gems to sell for gold. You could also swap gear to a temporary character, and face T6 bosses with your Level 1. On T6, it’s about an 80% drop rate. This will take roughly 5 runs, but killing the boss will be a bit slower.
Darkening of Tristram approach
If the season starts in January, there’s farming The Butcher and Skeleton King in the Darkening of Tristram approach. Not sure of the drop rate there, but I assume it’s the same. However, killing the boss has a potential to drop all 7 shards at once. This will cover your gold, and a fairly good chance at getting a diamond. This will be the fastest approach to getting the altar unlocked.
Through multiple tests on the PTR, while I could hit 18 by the 10 minute mark, it was roughly around the 26 minute mark on average before I had the gems necessary for the unlock and for gold. With the Darkening of Tristram, this should be about 10 minutes.
Now, one other thing to consider about using your Cache. If you play multiple modes, remember that you need a separate cache for each node. HC, HC SSF, SC, SC SSF. So, if you plan on having characters in each, you’re looking at 4 weeks minimum.
The point of seasons is to bypass the leveling and farming process because an occasional soft reset is necessary to start over fresh, so the game isn’t boring and people won’t leave. Of course it is.
I cannot express how debased this game has become.
With visions, you can get a lot of mats.
Slow in the beginning and very fast at the end.
My answer would be: Some people play on PC and some play on console. 
Exactly - one more reason not to use the challenge rift cache for leveling up 