AddOn Authors and Raiders try to make raids easier by making AddOns to make stuff like WeakAuras and Deadly Boss Mods, but then Blizzard responds by making these bosses so hard that said AddOns are basically a 100% requirement in any serious raiding, and we're back to square one; the only thing we've managed to do is to place a burden on every player to download and maintain 3rd party *required* AddOns.
Eh... other than boss mods, which are basically stopwatches, there aren't that many "required" addons in WoW. Addons are a tool you use to tweak your UI. They're a way for you to make yourself a better player by tailoring the information you're being fed to your own individual needs. By having a UI that's delivering information to you exactly the way you want it to, it stops being a game of playing the UI and starts being a game of playing the content.
Now my WoW UI was extensively modified with each piece positioned and configured just so. Did I NEED to do that? No. Did I enjoy setting it up? Yep. It's fun for me. And it helped me to become a better player because I could devote my attention to situational awareness and raid callouts instead of watching various corners of my screen for debuffs or cooldowns or ground markers, all of which by default are nowhere near each other.
One thing I wish they would have nerfed is freaking Ravana.
He's a pain at first. But then you get used to him and realize his abilities are entirely scripted until the last phase. So once you know the dance, you just dance with him. Like Turin said, as long as about half your party knows what they're doing, you should be fine. Ravana is actually the HW EX primal I don't mind farming because I can basically just turn my brain off and go because I've done it so many times.
Since the only real issue with casual vs core play, is the fact many gamers chose not to improve themselves, which is also part of the game's fault by not challenging players as they're progressing, instead only shoving it at the very end so it was very much "optional" if you were actually good at this game or not, and as much as people have issues with reading that, just really look at how you can still clear content without much effort put into it outside of certain Ex Primals (Zurvan, Nidhogg) and 3.5 Savage Content (A11 and 12s requires good coordination.)
Well sort of... the game DOES ramp up the challenge if you progress via dungeons. Brayflox is a lot harder than Copperbell for instance, and Stone Vigil is a lot harder than Brayflox. But when people are leveling entirely by spamming PotD they aren't really learning much.
And that's not going away anytime soon.
The nature of a particular player to either improve or not isn't something SE can change. There will always be people willing to skate through with minimal effort. When it comes to challenging endgame content like savage, then it stops working until they can be carried. There's no use in complaining that such a player exists because they've always existed and will always exist. This is what statics are for.