Weaksauce, as you may recall, is a shadow priest, whose professions are enchanting and tailoring. I purposely took the absolute weakest character class and decided not to gear him, ever, and see how far he could go before play became impossible. The one thing I could do was to enchant his gear, but his gear had to be all white (nonmagical)--no greens (magic) or better (epic/legendary). I made one exception after he got a First Mate's Hat, which is a green but which contributed nothing to his playability otherwise, having bonuses which were not suited for his class.
When I left off with the experiment, it was because he'd reached the Borean Tundra in Northrend, and the going had gotten pretty tough--not really difficult so much as too tedious to be any fun. Even so, I leveled him to 81, and he was able to handle most of the creatures in Northrend without dying all over the place. But other things caught my attention and I left him idle.
Then came Battle for Azeroth and scaled zones.
With zone scaling, zones which he had previously conquered--such as Burning Crusade zones like Hellfire Peninsula--now scale to his level. Formerly, BC zones topped out at level 70, and most of the monsters in HP were about level 60. Now, they're all level 80, and he can't touch them.
Original WoW zones don't scale that high. Top-level OC zones like Eastern Plaguelands and Blasted Lands scale to level 60 (where they used to be 55-60 depending on subzone) and no higher. So I find myself in the unenviable position where my level 81 character is too weak for Burning Crusade and too strong for the original content.
Went back to Northrend and gave that a go; fought a level 79 zombie and got killed in short order.
The first thing I did upon signing in was to do the WoW Anniversary quest; while looking around at all the quests in Stormwind Keep I ended up going to Pandaria at level 81, skipping the Cataclysm zones entirely--and which, if he can't do Borean Tundra, would be fatal to him even if they don't scale--only to find that no, without gear he can't do Pandaria.
So, how far can a shadow priest go without gear? I got mine to level 81. It might have been more if I'd kept at it, but even at level 81 it was starting to get dull, and in the aftermath of zone scaling he sure as hell ain't going to go much further. I figure that if I were to run the holiday event quests (Thanksgiving holiday, "Pilgrim's Bounty") I could get him to 82, because he's like 80% there already, but I don't think it'd go much further than that.
Now I have a choice: I can either gear him and continue playing, or I can let him languish until I decide to delete him.
One thought I had, though, was to play him with gear from one expansion earlier than the one he's questing in. In other words, get him some Cataclysm gear to quest in Pandaria, then use panda gear when he's in Draenor, and so forth. (Or get some BC gear for questing in Northrend.)
We'll see, I suppose.