I do not, necessarily, agree. I believe you might be selling people's understanding of mana adept short, as well as misunderstanding what the real issue people have with it is.
I guess the main problem is that the mastery is very mathy and most players don't understand yet its impact on how to play the spec optimally. The main thing to understand about the mastery is that in between mana cooldowns you will want to use cycles in order of increasing mps in consecutive order, starting with low dps/mps and increaseing to high dps/mps the closer you are to mana cooldown. Choosing at what dps/mps level to start and when to switch between cycles and how to react to rng will be the major thing that will distinguish an average mage from one taking the spec to its full potential. For more details on the math behind this you can check http://elitistjerks....p5/#post1626750 and some previous posts by Roywyn and Muphrid.
Needless to say, the points you raised were already addressed in the very same thread you linked. Let me recap some of them here:
1. The core idea of mana management through Mana Adept and rotation management (and through extension, the idea of altering DPM cycles) is reliant on the fact that there do, in fact, exist a selection of reliable DPM cycles to choose from. I.e. there is no point in stating "mana management and dynamic play will occur by selecting different cycles" when the actual choice of reliable cycles is almost non-existent.
2. As shown by me in post #430 of that thread (page 18, second paragraph), there are multiple fundamental flaws in basing the entirety of Arcane's mana management gameplay around a proc (especially since, there are no other tools to use for management).
The first problem is that, contrary to your assertion, it is actually harder to distinguish between a mage who played poorly and one who just got unlucky. (as shown in my post).
Secondly, the entire concept of the core gameplay of a "mana control" spec being based around a proc (hence "chance") seems to go contrary to the basic idea of what "control" means (as well as being slightly absurd altogether). It is like saying, "Frost mages specialize in freezing things" but then having the entirety of the "freezing" gameplay only happen through the frostbite talent (and take away everything else).
Furthermore, RNG as a "core" mechanic of a spec is really not acceptable. It may seem 'fun' or 'neat' when studied in a bubble, but as many a fire mage of early WoTLk can attest to, having the entirety of your performance be determined by RNG just makes for a frustrating experience. After all, telling a mage that he's S.O.L because he didn't save up enough mana because the RNG-gods didn't smile on him isn't exactly the most robust system or design for a spec to have.
3. And probably most importantly, many people do not have a problem with the core idea of mana management or even mana adept as an idea per say, but instead, they have a problem with the fact that a spec that is 'supposed' to be about mana management doesn't really have many tools to manage that mana with. I would go further and assert that even if, somehow, arcane rotations were fixed to give us a large (and diverse) toolbox of rotations to choose from, that should just be one of the ways Arcane manages mana and interacts with its mastery.
This entire idea is encapsulated in a very simple yet potent statement made by Pasture in that same thread:
Well the dynamic element of the Arcane is supposed to come from its mastery, ie maintaining high levels of mana for as long as possible. That in itself is management enough without adding lots of tricks and complications throughout the tree. The main problem with this is that Arcane doesn't really have anything new to manage with.
The basic idea is, that you cannot base a spec around a core idea, but not provide a diverse set of tools and gameplay options to interact with that idea. Fire has numerous talents, abilities and combos that play with its DoTs, that effect its DoTs and that alter/extend the usability of its DoTs. Ditto for frost and freezing. That is the real issue people have with arcane.
So no, I do not think that the reason people are having trouble with Arcane is because they don't understand the mastery. In fact, very early on, many mages intuitively reached the very same conclusions about altering DPM cycles that Roywn and Muphrid did later in that thread (remember, you do not need to build an optimal theory model to be able to 'understand' something, even if just on an intuitive level, which, for Mana Adpet's case, is more than enough).
And all this is without even going into the issues people have had with the fact that Mana Adpet will inherently be a grande sized pita to actually balance right. An idea which alone makes people weary of mana adept right now. The lack of any real changes to Arcane in numerous beta patches does very little to alleviate this weariness.