You spend 20 hours a week in raids. That, in of itself is a huge amount of time. On top of that, you are actively participating in the theorycrafting community beyond scribbling a few formulae on a table to determine if you reforge in the direction of haste or mastery. Which is good, and it is excellent to see people get so engaged by something but that likely eats up a considerable amount of time which certainly isn't factored into your raid times. Then on top of that you likely do dailies, perhaps a little PvP or pet battling on the side?
All in all, that is a massive amount of time you are sinking into the game and heroic raids are your thing. That is fine, they used to be mine as well. However, due to RL circumstances, I am lucky if I can sink 20 hours into the game every two weeks. Raiding for 20 hours a week is something I don't have the luxury for anymore. I would adore to be able to do some sort of challenging but not incredibly frustrating content but given my playtimes and the guilds that I end up being able to raid with as a result I am one of the people sitting at a half way point.
With LFR being far too easy and ToT normal being too difficult for the group I am playing with - I have more wipes on council 10 man normal than I do over Mimiron 10, Mimiron 10 HC and Mimiron 25, more wipes than on Kalecgos, more wipes than on Brutallus who ultimately forced the guild I was part of to realm hop - I am one of those awkward, average subscribers that simply isn't having the best of awesome fun times at the moment. You are coming from a fantastic perspective; one where your time commitment and / or skill allows you to progress well. As outlined though, you are certainly within the 0.5 % of the playing population and, from experience, it is very difficult to see things from the other side of that bubble until you are suddenly on the outside.
Do normal modes need to be easier? Perhaps, though only slightly - I tolerated learning Shade of Aran for a month when I first started playing the game. Normal modes certainly need to be curved better. The current difficulty is far too punishing, far too early.