Newish player here, so my opinion will be limited to what I've learned in a few months.
Starting right after Aether Revolt
release, I was knee deep in energy card potential, loved the possibilities. Looking at older mechanics with counters: +/-, time, age, loyalty, spore, etc - there was always a card to modify or mess with those counters, and I was really surprised that there are few, if no, ways to fiddle with energy counter totals, even punishing a player for gaining energy.
I think it is because the energy producing cards are in most cases already heavily priced in terms of mana or utility aside from energy production - gotta pay to play the energy game. Also, they are powerful enough to not need many boosting effects. Like in all mechanics, there are some 'broken' cards, in that they are more advantageous or less costly. Like most successful theme decks, energy decks have to sacrifice in some areas to go all in enough to benefit from theme.
When it was saheeli / felidar, that ban needed to happen...after a very long period - and many of those same folks thought Gideon too needed the hook. Those were the key cards in the 2 dominant standard decks. But it has been proven out that Mardu Vehicles was only as dominant as it was because it was best at Copycat and the best toolbox to deal with the rest that had to warp their decks to compete with copycat. Now that Mardu Vehicles has to stand on its own against decks free from turn 4 death...other themes are making their mark.
I think talk of banning Marvel is a little too soon, seeing as it is far from unstoppable, and especially when the big bad eldrazi will be
gone soon.
Oh. Bolas. Well, my other points stand