I haven't mentioned the rest because I couldn't see a point. I don't even understand what you mean by boosting. Do you mean that engines are creating boost points over time or that somebody plays one big boost?
Whatever you mean: both things were present in beta.
See, I don't even think that boosting is the right verbage, because it mixes up strategies that are very different in their core. If you look at beta, your word boosting would apply to old nekker decks as well as old spotter decks, but they were not the same. One deck won by building up points over time while the other one won by bringing a lot of points quick.
Same goes for hc. Boosting can apply to a way of carry-over. It can apply to forms of engines and it can apply to tempo. These strategies are very different and by calling all of them just "boosting" makes diffent ways of play look just like one thing. It isn't one thing.
You can't see the downsides of various strategies unless you experience them yourself. If you think that silver-witchers and roach are OP in R3 I would strongly recommand trying to integrate this combo in your deck to see how it really plays out instead of complaining other ones using OP strategies.
Same goes for the Eredin decks you hate. I have no idea which 12 points immue you talking about, since I've seen Eredins ability being applied mostly on Dash, Ciri, Sabbath or Ge'els, but whatever it is, try it out yourself to see how much good execution has to go into setting up those plays.
I strongly think that you just don't see how much your opponents pay to execute their combos in R3.
The Eredin Deck I am talking about is mine. I use Frightener and Glutsyworp. Use Eredin's leader ability on Glutsy gives me a 16 powered Glutsyworp Immune and a 12 powered Frightener Immune. And then I use the cards that damage if I have the highest powered monster and because neither monster can be targeted it makes it difficult for anyone to break through. Beside Skell and all their "deal 8 damage among Random enemies".
And I already stated the Witchers was a personal distaste of mine. I already admitted that. I was merely pointing out that everybody uses it. I don't like the Witchers because I'd prefer to see more clever ways to win.
And I disagree, Boosting to me is turning any powered creature from its original power to another power. Doesn't matter how you got there, you Boosted a 3 to a 12 somehow, someway. So Boosting no matter the R3 strategy is still technically the same.