Finally, someone who appreciate the nuance (or rather, the un-nuanced use) of the “RNG” meme…I share all your concerns (heaven forbid card/ deck-milling is ever introduced into Duelyst shudder) and add my conclusions as follows:
That last thread got de-railed/locked because posters got “triggered” by each other into a cyclical feedback of knee-jerk reactions and refused to accept/understand what each other was talking about in terms of “RNG”. So I’ll use TCGs with a completely different system as an example, so that I won’t trigger anyone:
In TCGs like Magic/ Hex/ etc. where the mana/resource needed for playing “costed” minion/spell/etc. cards must also be drawn and played, players must accept the possibility of mana-flood (only drawing resource/mana cards) or mana-screw (not drawing enough mana/resource cards)-- which causes clueless players to instantly fall back on the “(too much) RNG” meme.
But the inclusion of the no. and type of resources/mana cards is part of the deck-building process under the player’s control, which actually adds skill/complexity into planning of the mana/cost-curve of costed cards. With auto-mana/resource generation (and without other game mechanics) the game could easily be reduced to “deck-building + top-decking” because you can largely plan for the limited scenarios that can happen in-game.
This is where I pause and ask any reader here to remember (and ACCEPT) that there is NOTHING inherently “good/bad” about RNG-- it’s all about the differences and nuances in vision and execution in each particular game/instance
Hearthstone went heavy/ crazy with RNG-effects in their cards because their deck has only 30 cards and their board has only 7 minions a side-- so there is literally nothing else to prevent the game from becoming stale/solved as they are determined to keep up the tempo and brevity of their game.
OTOH, Hex with a deck and board of unlimited size (your PC capability is the limit) has precise card text multi-paragraphs long because on top of deck-building and mana/ resource-generation planning, it has already given players plenty to do with multi-phase turn-taking (player declare attack, opponent declare defense, etc.-- not to mention “interrupt” cards available to both sides) as well as a discard pile to interact with…
The theme I getting to here is this: the kind of interactivity/control a game gives its players determines the kind of players they attract (no, I don’t mean “aggro/control/etc.”-- it’s much more nuanced than that)-- sort of like the way FPS and 3rd person shooters tend toward different players, or at least different kinds of gameplay.
All cards/ mechanics, including RNG-effects, introduced in a game will be seen by players as a challenge to be “mastered” in their attempt to beat the game or other players-- an RNG-effect too crazy/weird to be “mastered” (or cannot be “answered”) will simply be rejected by top-tier players who can get to where they are only with consistency, consistency, consistency… and a game-changing card/mechanic rejected by such players will cause them to reject the game.
Which is not to say there isn’t a place for special needs/ interest cards like Groovy Lion in gimmicky/ fun decks like Solo Vaath.
TL;DR: An expansion is just that, an expansion-- whatever fails to work with the existing game/ cards (and trust me, people will be experiment/ testing the hell out of it) will be rejected with the equivalent of an “ignore/block”-- so the game developers will know by the game stats (and popular strategies) they track, how well a new card/ mechanic introduced has actually been “integrated”… if pure theory-crafting can tell developers how much RNG is “too much”, there would never have been any patches/bans/etc.