Hearthpwn

These are all very valid questions and i'll try to answer them as best as i can. But really, if i had a recommendation to give you on how to get the hang of the basics i would say to pick a straightforward budget deck that's out right now and getting to understand its game plan as a foundation.  If you're building decks on your own right now it would be hard to ascertain if games were going south because of inefficient plays or because the deck wasn't built properly, so using something already established to be viable would let you focus on how you're playing the game.  For instance, since you're saying shaman is a class that's interesting to you right now,  murloc shaman is a good aggressive deck that is affordable and also easy to understand.  I'm gonna try to use it as an example to answer the three problems you highlighted.

1. So, for mana cost, it's actually relative to the type of deck you are running but a general rule of thumb is to maintain a reliable curve, as in being able to play cards efficiently on most turns without bricking or doing something way too weak.  in most decks, you want to be able to have a 1 cost minion first turn to establish board space, a 3 cost card on curve, and then a healthy balance of cards you can play together on later turns that synergize. However, it's most important to consider what it is your deck is trying to do, and whether higher cost or lower cost cards fit that game plan. Using murloc shaman as an example, it's a deck that runs a lot of low cost minions,  more than a typical deck, to establish a big board early and close out the game with a finisher (Bloodlust) to hit the opponent directly with a ton of damage. Like, this is a deck who's dream scenario is closing the game out by turn 5 or 6.  There are great cards that shaman has, such as the 8 cost Walking Fountain, that make sense in other late game shaman decks but don't fit in aggressive builds like murloc.  So, your mana distribution is really just reliant on what the purpose of your deck is and whether it benefits from high or low cost plays.  

2. Archetypes, although they're very common in the basic set, are actually not as relevant as they used to be.  you'll see tribe based decks get popular every once in a while, but it's not a main focus per se.  It's important not to fall into the trap of running bad cards just because they're a part of your archetype.  Like, if you want to run beast hunter, even though Silverback Patriach is a beast, it's better to run literally any other 3 cost card because the card is so awful that it will lose you games even with all the synergy in the world.  I would capitalize on effects that work off of one another before a tribe. However, murloc shaman is an exception to this, as it actually runs a lot of murlocs that aren't typically "good", and that's because Underbelly Angler is an insane card and it generates huge amounts of value in your hand off of 1 cost and 2 cost murlocs.  

3. A spell to minion ratio is also something that depends on what the deck does, and where those terms you mentioned like zoo, control, etc. come into play.  To explain it in very basic terms, there are decks like control, that want to remove all threats from the board as often as possible, so they run plenty of spells and removal in order to exhaust the opponent of their options.  Aggro, on the other hand, wants to close out the game as early as they can, so they typically run more cheap minions and a low amount of spells in order to keep up the pressure and end things quickly.  Really, what you want to do is make sure the spells you run are useful to you and are cohesive to the goal of your deck, as opposed to how many there are.  Like in murloc shaman, you have the option of running great removal spells like Earthquake, Hex, etc. Now, earthquake obviously has a great effect, but it's also very expensive for an aggro deck.  In fact, you really might want to run Earth Shock more than the other options because it's incredibly cheap and can silence a taunt and let you get back to hitting the opponent's face without sacrificing your whole turn, even if it doesn't actually remove the minion.  Essentially, what you want be thinking is "which spell is giving me the best deal mana-wise to achieve what i need to do in this deck?" when picking your spells.

As far as duplicates, it's pretty simple: if the card has a fair mana cost and works really well for your deck, meaning you want to see it more often, put two copies in.  You want to run two copies of your best 1 cost card and 2 copies of your key mid game cards in most decks.  Like in murloc shaman,  you need to see underbelly angler as often as possible, 100% if running 3 copies of that card was allowed people would do it.  This only gets tricky when it comes to big late game cards, as you might still want to run just one so you don't see it too often in the early game and brick.  

as a final note, i think the people above me make a good point in that reading all the meta terminology on this game is kind of unnecessarily confusing.  I think the best way to get acquainted with decks is to face them in game and catch on to what they do as you see them being played.  i didn't properly understand what combo was until i saw a priest bring me from 30 health to 0 in one turn, and i also didn't get what  control meant until i saw a warrior wipe my board four times straight until i had nothing left to play.  It's seeing them in action that really helps it click and tells you "oh THIS is what this deck does" but you also learn what you did wrong and how to counter their go-to strategies.  It really just starts making a lot more sense when you face similar decks over time and see the common thread in what they do. 

For omega assembly, i think the discover mechanic change might be enough. There's still cards like zilliax or snip snap which will suck to see more often, but the more mecharoos/skaterbots they get the better for the rest of us.

On slam, i agree 100%. It's ridiculous that a class with such a gross amount of mass removal also gets plenty of spot removal with this, execute, and omega devastator. idk how much more fair it will be if they start running 2 executes instead, though

I agree with you that it's one of the most popular and least interesting decks out right now, but not the strongest. I think atm priest has the most degenerate deck and inner fire/divine spirit are up next for a drastic change, or more likely even to be removed from standard. The team is really obsessed with class "identity" as of late and i can't see anything more opposed to that than combo priest.

Imo it definitely is. One of the best hero power options is less likely to pull devastators/tomb wardens/dyno-matics with rush, and a card they often save until turn 10 to get up to 3 class cards to use with their rush ability is less effective as well. 

Looool i was tripping out looking at your warrior decklist  because i had forgotten that Hench Clan Thug isn't actually a Rogue class card

Tess Greymane 🥺

Calling someone dumb based on a singular, pretty reasonable response seems, well... dumb.

Nerfing a rogue card that has been in the game forever cuz of a new card,thats kinda pathetic.Balance the new cards around classic cards,wtf... There are matchups where u kinda have to allin with a big Edwin,leaves ur hand empty,and often not a bigger body than 8/8 or 10/10 on the board on turn 3-4-5,with a million counterplay to it-secrets,poly,hex,silence,all that stuff.Its a high risk high reward play often,but u can lose the game on the spot,depending on ur next topdeck..Surely needed a nerf,at least u can counterplay druid with corrupted clowns after the +4+4 buff,thats kinda balanced.Also nerfing a shaman weapon by dmg when it wasnt the problem,it was the durability that gives u 2 turns of rng evolve,even an 5/1 weapon would be a better nerf...Damn,even Blizzard dont understand their own game at this point im starting to think..

 Just add every tech card in the game to your deck and hey presto, you'll beat every deck ever created!

Yeah looks like it can be fun. :D 
From what I read from other users below these seem like fun targets. 

Flik Skyshiv 6 mana, this 2 mana, shadowstep this, Flik Skyshiv 1 mana, this 0 mana, 1 mana Flik Skyshiv. = 10 mana kill three enemy minions permanently. (and with one more shadowstep you can keep this or play another Flik Skyshiv next turn) 
Heistbaron Togwaggle, this + shadowstep = 10 mana, three Heistbaron Togwaggle effects. (Also an extra time next turn with another shadowstep) 
Kronx Dragonhoof, this + shadowstep = 10 mana, three Kronx Dragonhoof effects. (Also an extra time next turn with another shadowstep) 
Leeroy Jenkins, this + 2 shadowstep = 10 mana, 24 face damage. Or with some prep to cheapen Leeroy or this before, then you can get 30 face damage in one turn….
Tess Greymane, this + pre shadowstep + shadowstep = 10 mana, three Tess Greymane effects.

With some other cost reductions cards and/or coins you can play
Dragonqueen Alexstrasza two or three times in a turn.
C’Thun two or three times in a turn.
Yogg-Saron, Master of Fate
C’thun, the Shattered

Only a panda can powercreep pandas

Hearthstone now is to zoomers what casinos are to boomers. And that’s pretty fucking sad.