You must think at all elements. For example, if you ban Time's Dragons and Ghosts you basically turn the game into a stall. I think I'll ask the future Masters what they think though, as them should know better.
The difference between the Masters' Tournament and Trials is that here you are facing an opponent of the same element. So, forcing your opponent to use a stall is not nearly as bad. In Masters' Tournament it was a problem, because eg. Fire can force you into a stall, then bolt you/fahrenheit you to death. With mono it was kinda hard to counter, because they only need to ban one card (now 2, after the addition of GotP), while you'd have to ban 2-3 to counter it.
On the other hand, during trials, the fact that someone can force you to stall always means that you can also force him to stall, thus it is a balanced solution. If you ban eg. Aether's Phase Shields and Lightnings thus forcing Aether to 'rush', it is also balanced because your opponent will always be able to do the same to you.
Although it might be quite boring, limiting the available decks like that.
But... the 50% off-element rule, or anything similar 30% off-element etc. solves the problem.
As for SoG, I think it is auto-banned in too many PvP events. Some stall decks need SoG to work, and I don't see a reason why those decks should be banned from nearly all PvP events, as long as they are not brokenly OP. And personally, I find quantum denial decks to be much more boring to face than SoG stall decks, so I'm not sure why so many people accuse SoG of making boring decks. TBH I enjoy pwning SoG based rage quit decks, while quantum denial is the only thing that could possibly make me rage quit.
In other words, it's much better if SoG can be banned strategically, but does not have to be. I would usually ban EQ and Discord before SoG, for example, since with a proper Time stall I can outdamage even Permafrost+6*SoG, while EQ and Discord are much more likely to cause trouble to both Time stall and Time rush.