Alright, here we go
Creative ideas and OP cards
The problem that the Expanded format is facing for quite some time now, is the lack of any rotation. Sure, eventually the early BW sets will rotate out of the format and in a couple of years we'll probably look at a XY onwards format, but that would mean that cards from the later XY expansions (such as Hex Maniac and FogP) will stay in the format until the end of times.
The problem with a card like FogP is the difficulty in trying to balance two vastly different formats. With FogP in Expanded you'd force the designers to tune down any strong grass type evolution, in order to avoid a scenario where said card can be used to break the Expanded format. Likewise, this is also difficult for other card types, because if you can't print a strong grass type evolution line you'll automatically strengthen Pokemon with a weakness to Grass (as those decks would become inherently weaker than the rest of the field).
It's important to keep in mind that we are talking of high level competitive here, where anything but the best will be discarded.
Hex Manaic has a similar issue. With the card lurking around in the Expanded format you quite frankly stifle any creative attempts to integrate new Pokemon with unique abilities into the format. Imagine a deck like Rotom in a world where Hex Manaic is viable. Yeah, fun times.
Lets take a moment to talk about Zoroark GX. You'll probably remember a deck called Caw Blade (at least that's what I remember it as). The name was stolen from an older MtG deck that dominated the Standard format and likewise this deck went nuts in the Pokemon Standard format. Consisting of Yveltal EX, Zoroark (acting as a non EX attacker, Keldeo substitution and occasionally Zoroark Break / Nasty Plot Zoroark for a surprise OHKO) and Gallade (Maxie's Hidden Ball Trick).
The deck became immensely popular, spawning several versions (sometimes dropping Gallade for Garbodor) and pretty much dominating the format.
Well, as soon as Zoroark GX was printed the card continued the success story.
The biggest asset of the deck was the draw engine, that allowed you to run disruptive supporter cards and still be able to get anything you need from your deck. There was also quite the broken synergy between an opposing Sudowoodo and Eggs. You pretty much run 3-4 Eggs in most versions, because they could be used to power up your Sky field bench quickly. You'd get them into your hand, play Hex (thus disabling the Sudowoodo), then drop your Eggs and OHKO the oposing Pokemon. On your turn Sudowoodo would become active and you could simply discard your eggs and start all over.
In the mirror this became quite ridiculous, because once you were in the Hex lock you couldn't use your own Zoroark, and don't get your Eggs back. However, playing your own Hex would disable your own Sudowoodo, with in turn would result in your opponents Eggs staying on the field, increasing the opposing Zoroark GX's damage. On the one hand that created some pretty interesting game states, on the other hand it was freaking ridiculous.
The biggest problem with a midrange deck like Zoroark was the fact that it was so oppressive. With the ability to easily tech in cards like Mew EX or Garbodor to deal with fighting types, easy access to Enhanced Hammer and the above mentioned combo of insane draw engine and disruptive supporters, the deck could answer anything that was thrown against it.
With the ban of Puzzle of Time (another huge asset in the archetype), Hex Maniac and the printing of Faba in the latest set Zoroark has become just a good deck (currently often run in conjunction with Magcargo, to enable a multitude of tech cards), but considering how much they threw against it, I think that feat alone speaks for the strength of the card.
I'm falling asleep
One argument that is often overlooked when it comes to the ban of Hex Maniac: The card was simply not fun. Now, I know what you are thinking:”We are talking about a competitive environment, I don't care if my opponent has fun, I just want to win.” Thankfully I agree 110% with this and if it was simply unfun for the opponent to play against I honestly couldn't care less.
No, I'm not talking about the fun for the players, but rather the fun of the spectators.
The initial time of S&M was quite interesting ,as new decks emerged and every tournament saw an interesting new tech being added to existing decks. Expanded on the other hand was just boring and sometimes painful to watch. Between Trevenant lock on turn one, Ghetsis and and endless barrage of Hex Maniac, every game went to a full on attrition war. I witnessed many different iterations of the game over the course of the last 4 years and I can say without a doubt that this was by far the worst to watch (heck, even the time with LTC in the format, were you would watch Seismitoad just draw his entire deck, play LTC and then proceed to do the same turn after turn was more fun to watch then this).
I don't know how the viewership numbers compare between the two formats (which is probably difficult to measure anyway, since the majority of the regional tournaments are Standard anyway), but if the idea of Expanded is to present that huge open format with a lot of cool cards, than quite frankly you need en environment that supports fun and creative (and insanely strong) decks.
The shadows of the abyss are like the petals of a monstrous flower that shall blossom within the skull and expand the mind beyond what any man can bear, but whether it decays under the earth or above on green fields, or out to sea or in the very air, all shall come to revelation, and to revel, in the knowledge of the strangling fruit - and the hand of the sinner shall rejoice, for there is no sin in shadow or in light that the seeds of the dead cannot forgive...