I'm a bit confused with the Rose quests. I have got to the one to find a key fragment at Blackwater mine. I'm level 18 but the mobs are all 40 and rip me to peices. I saw a few videos of this place and the mobs are all around lvl 10. Do I have to do other things until I'm a higher lvl or has someone else spawned high lvl mobs?
If you've seen videos of other players finding ~L10 mobs there, then it's almost certainly due to someone else spawning high level mobs. I've encountered that a number of times myself, with areas that commonly spawn L10-22 mobs suddenly spawning L60+ mobs on a visit there. Not a good game design decision, but that's FO76 for you.
I'm a solo explorer type of player, so I'd explored the entire valley area before going elsewhere. I was >L30 before I encountered Rose. I still haven't even done the first of her quests because it's in an area I haven't been to yet and I wander off to every unknown location that appears on my compass, gradually moving further afield. So I'm fine with unexpected spawning of much higher level mobs - at L40 I can solo a pack of L60+ mobs with no major problems unless one of my weapons breaks.
[..] Also I have a steel undervest which looks well dodgy like S&M underwear
but it adds +1 Endurance at all times
Unless you're wearing power armour. Power armour negates all bonuses from everything else you wear. I have crafted modded underarmour that adds to stats and it only applies when I am out of my power armour. That's a design decision by Bethesda, no way around it. You can confirm it by checking your stats in and out of power armour (as I did).
Outside of power armour, I'm wearing Mothman cult ritual bindings, a ranger hat and cliched USA motorbike cop sunglasses. I look wonderfully strange out of power armour. Utter nutjob territory. I smile every time I craft something. I'm going to take some more photos when out of power armour, just for jollies.
I'm not trolling and there's no need to be defensive, it was an observation that a game that's been heavily criticised in reviews and has received a stream of criticism from gamers and the gaming press since release is outselling well-received titles that came out at the same time, prompted by the person before me saying they're buying a copy "just in case it gets fixed".
It sells predominantly because it's a Fallout game. Bethesda could throw out any old turd with a Fallout skin and it would sell at least quite well for a while.
Most of the criticisms I've seen are valid. There's some hyperbole, but there's a lot more of that from the fervent fans (as you can see in this thread).
The game itself is deeply flawed, for the reasons widely stated. However, there's somewhat of a dichotomy. The world-building has been done very well, with an abundance of notes and environmental storytelling in the usual Fallout manner. The construction of the external environments is arguably the best yet in a Fallout game, though that's possibly down to the novelty of a rural rather than urban setting. The flaws are in the fundamentals of the game design and in the foundation of the game. Bethesda have no relevant experience in an online only game and it shows - load times are farcical, lag spikes are ludicrous and reliablity is well below standard. The lack of modding is another massive flaw as modding is a huge part of Bethesda games (to fix bugs, to work around bad design decisions and to add huge amounts of content). Although there are at least 2 mods that fix a couple of the abysmally incompetent UI decisions that Bethesda made - one to make power armour headlamps less crap and one to make inventory management less crap (it allows you to seperate food and drink from the rest of aid and to see the combined weight of stacks of items and of entire inventory tabs).
If Fallout 76 was a house, it would be one that was well built by skilled builders but with substandard materials and bad architecture and badly positioned. Like such a house, it's not worth full price but would serve some people well at a reduced price. I have found it good value for the £27 I paid for it. At the current PC price of <£15, I'd certainly say it's worth a try. Some people like it, so I think it's worth betting that much on liking it. There's some good stuff in it and some good stories in it.
I think a lot of the vitriol stems from the fact that it
could have been a much better game and some people are angry at the bodged job and worried that this is the future of the Fallout franchise (which would kill the franchise) rather than an experimental side project (which I hope it is).
If FO76 was an entirely new game without any previous Fallout games having existed, I think the prevailing view would be that it was a promising first attempt with a lot of potential for a better sequel.
Admittedly though I should have actually posed the question of: Is it now in a notably better state since those reviews
No. There have been some minor tweaks and a few of the bugs have been patched. There haven't been any fundamental changes and there probably never will be. It is what it is. They might improve stability. They might fix bugs. They might improve performance. But they can't change the fundamental design of the game and that's the biggest problem with it.
I did not leave the game its still a little buggy obviously as it said you were stuck on the main menu from my side of things! Also I have a steel undervest which looks well dodgy like S&M underwear 
