I am a classic player, I am trying retail.
I’m curious about retail warriors’ rage generation. I read that we get rages from white hit only. The classic warrior class has insane scaling from stats like crit, hit, expertise. The more white hits, the more rage, the more heroic strike we can pump.
How does rage work for retail warriors? Do we have the same double-dip positive loop that makes warriors stronger as we are more geared? Do we get less rage against plate armor class?
With arms it’s pretty much just crit hits (with a bit of haste to back it up) that generate rage all while throwing in a charge here and there to keep the attacks going and using slam primarily to prevent capping rage and ms on cd. Fury, haste is your primary friend with auto attacks and all of your abilities generating rage in some way and dumping it all into rampage.
As for rage against certain armor classes that’s not a thing on retail. You generate rage the same way against everyone else.
Rage generation is fine 
I’m not sure about prot, atm. The last time I played it was in WoD for shenanigans in pvp with a certain talent 
Arms generates rage from auto attacks, primarily (or talents). The shift at level cap is that you get “free” attacks through Overpower resets (since OP doesn’t cost rage), and Execute on Sudden Death procs (or you can talent Skullsplitter, which generates rage). The spec is about managing your rage spending to ensure you can always Mortal Strike on cooldown (or pool for Ignore Pain if a big hit is coming).
Fury is a generator spec, where basically everything you do builds rage, and your only spending options are Rampage (big DPS chain + Enrages you), and Ignore Pain (defensive spender). AAs also generate rage, but most of it will come from your abilities themselves, and it’s GCD-locked with Whirlwind as the filler when nothing else is available to use. The spec is about preventing rage capping while maximizing generation and Enrage uptime.
Protection is also primarily a generator spec, with most of your rage coming from Shield Slam (and Thunder Clap, with supplemental from AA), or cooldowns. You spend rage on Shield Block or Ignore Pain to mitigate, or Revenge as an offensive AoE dump (and Execute as a ST option at 20-0%).
Windfury ends up being a huge buff to Arms, since it procs white hits that generate much more rage. Since Fury’s AA buff it helps them more than it used to, but still nowhere near as much.
Arms slaps in shadowlands, feels really good right now and I see quite a few arms topping the dps charts in raids. They’re in the best spot they’ve been in a long time.
Gameplay wise your’re managing rage between spenders and generators. As long as you don’t go crazy on your filler it’s pretty smooth.