Erm.
Timewalking gives you a piece of normal gear, there’s pretty affordable crafted gear you can fill one slot with and you don’t need a high IO to get into M0s and low M+. Sure, you’ll find idiots gatekeeping some of those low keys and other idiots starting to try and farm valor early, but with some elbow grease you’ll get in.
Otherwise, move over into the slow lane, build up your Cypher levels and eventually the gear will be 252.
M0 drops the same level as cypher 1 gear. And I humble suggest you try getting into m+ with zero io and no connections before you say you don’t need it to get in. The one +4 SoA I managed to get invited to poofed before it even started with “having trouble with my internet connect guys, try again later.”
EDIT - and I stated before the ONLY pieces of gear I have above cypher/ZM rewards are the weekly TW reward and one crafted 262.
I did it back in 9.1, except I did it from my bootstraps. I did M0s during a Dungeons week, then just did my own keys. It’s not some herculean effort to start in the 0-2 pool and work your IO up the old fashioned way.
You know what helps when you complain about gear?
Posting on the toon you’re having trouble gearing, or linking their armory.
So people can see what you have and offer personalized suggestions.
That said, the dune rares definitely drop 246 weapons.
Not once in 2 weeks for me they haven’t. I have gotten exactly one drop on each of my two mains at 242 (one got a cloak and one got boots) in 2 weeks and nothing above that. That is running around ZM for several hours per day and targeting the ones that drop weapons for my classes. I have basically given up on one of them and am focusing entirely on my DH and haven’t seen a single drop in 3 days. Everything WQ/Daily has been a dupe.
Do you need to be 24/7 on ZM to get ilevel 246? I just started ZM. I was on Mythic+ 5/ +6 for few days then I started ZM. The highest ilevel gear I got from ZM is ilevel 236. Maybe it was just luck. Maybe I need more time for ZM. BTW, I just came back to WoW last Wednesday. Pretty rusty but I think I can now handle higher M+'s.
A chunk of the gear from ZM is based on your Cypher of the First One’s level. So you need to work on that, either by doing dailies, chests, grinding rares, etc and also work on your rep with The Enlightened.
ZM is not an alternative path to M+/PvP/Raiding.
The weapons from the 3 dune rares can only drop at 246.
Cypher Gear requires doing Cypher Research to get a higher base ilvl for them, so yes you’ll need to play a decent amount for that.
That said, there’s also the Desert Relic gear that’s 246 if you only have limited time each day. Gather Sandworn Relics from killing Mother Phestis, Garudeon, and when they’re up, Akkaris and General Zarathura.
At how slow gathering those Relics are, without grinding the chests, I really wonder if your regular Cypher gear will be better/equal by the time you get enough to really get those pieces.
The relic gear is beyond useless. 300 relics for anything beyond cloak/bracers. You will have cypher 3 before you can even afford 1 piece.
I have yet to see a quest or daily that have a weapon as a reward, mostly its armor, ring, or trinket. I was fortunate that it only took about 3 days of farming the 3 in the dunes to get what i was looking for on my DH. The hunter, not so much, about a week and a half. Got weapons that may suit survival although i play BM and finally got the crossbow. All at 246.
That said, you have your first kill of x boss to rng a drop you want for that day, anything more is just farming for cyhers, etc. Go to the ones that may not have your preferred stats even if its ilvl youre concerned about and rinse/repeat the next day. It sucks yes, my DH went through just about the whole tier of sanctum with the upgradeable korthia at max 233, only to get an upgraded weapon on patch day. I couldve farmed mythics for stuff, i just liked raiding better as my preference.
At cypher 3 you should be seeing cyhper gear at about 236-239 for that type, the cost of the vendor gear is a real kick in the pants for sure.
There’s only one weapon that matters in Zereth Mortis:
Ive got the wrong class(es) to even loot this thing, hell guess I’ll have to play the DK after all. There can be only one.
You want to hear the best insult to injury? A week ago I got the green lightsaber… on a non-Int class.
yep there is a bosses that a drop a 246 wep, seeming at a 100% drop for everyone EXCEPT ME BLIZZARD!
Nah the best insult to injury was me. Waiting there for them to spawn everyday til yesterday on my arms warrior then when a wep finally did drop from them… it was a shield.
Ow, as bad as afformentioned hunter. Those 3 bosses weapon drops do not account for spec, so it can be a wild ride. You got a pretty cool mog though, i got the purple-ish tinted one from the engulfer rare and have the 246 weaps mogged to it, look pretty ba with the necro enchant appearance on it.
Looking over these for Rogue weapons. I don’t see much.
Gluttonous Overgrowth drops a Fist weapon called a Punching Dagger and Xy’rath the Covetous drops a Sword. All other weapons are Int, STR, or two hand.
So no AGI daggers at all? 
The desert area has 2 agility daggers that have a set effect. I remember mousing over them on my Handy Notes.
The ones in that article only show the more unique weapons… IE - the popular ones. The laser fist weapons, laser swords, etc.
Unless you break down each rare, it’s kind of hard to know. As Cinder said above, Handynotes does break it down on your map, but I don’t have that enabled.