For the first expansion;
You can progress up to solo tier 10. Meaning there are 10 zones, or otherwise things you can solo progress through. You will likely receive your Artifact Stone 4 in Solo 5, and your Artifact Stone 5 in Solo 10.
You can progress up to group tier 5. Meaning there are 5 zones, or otherwise things you can group progress through. You will likely receive your Artifact Stone 4 in Group 2, and your Artifact Stone 5 in Group 5.
You can progress up to raid tier 1. Meaning there will be 1 zone, or otherwise thing you can raid progress through. You will get your Artifact Stone 4 and 5 in this zone.
Now the real question; Will you be able to solo group tiers or raid tiers at any time, the answer is; maybe. Below is how I want it to be designed...
Solo tier 10 *should* be able to solo up to group Group tier 3, maybe tier 4 if you're lucky, but very unlikely tier 5. That being said if you're full Group Tier 5 you likely won't be able to solo Group Tier 5 because of mechanics and other things that interfere with your capability to solo it. With the 50% HP potion you might be able to down a few bosses, but not the end boss.
Raid Tier 1 *should* be able to solo all solo and group content with a full set of gear, with stones and what have you. Meaning if you obtain a full set of raid gear you should be able to walk into Group Tier 5 and clear it with little to no issue. Specially with the 50% healing pot, you still won't be able to solo Raid Tier 1 though, the abilities and such bosses cast will be too much for you to solo, maybe group, but not solo.
You can progress up to solo tier 10. Meaning there are 10 zones, or otherwise things you can solo progress through. You will likely receive your Artifact Stone 4 in Solo 5, and your Artifact Stone 5 in Solo 10.
You can progress up to group tier 5. Meaning there are 5 zones, or otherwise things you can group progress through. You will likely receive your Artifact Stone 4 in Group 2, and your Artifact Stone 5 in Group 5.
You can progress up to raid tier 1. Meaning there will be 1 zone, or otherwise thing you can raid progress through. You will get your Artifact Stone 4 and 5 in this zone.
Now the real question; Will you be able to solo group tiers or raid tiers at any time, the answer is; maybe. Below is how I want it to be designed...
Solo tier 10 *should* be able to solo up to group Group tier 3, maybe tier 4 if you're lucky, but very unlikely tier 5. That being said if you're full Group Tier 5 you likely won't be able to solo Group Tier 5 because of mechanics and other things that interfere with your capability to solo it. With the 50% HP potion you might be able to down a few bosses, but not the end boss.
Raid Tier 1 *should* be able to solo all solo and group content with a full set of gear, with stones and what have you. Meaning if you obtain a full set of raid gear you should be able to walk into Group Tier 5 and clear it with little to no issue. Specially with the 50% healing pot, you still won't be able to solo Raid Tier 1 though, the abilities and such bosses cast will be too much for you to solo, maybe group, but not solo.