D1 is surely not the Problem. If anything it was a well-made decision. All these hypocrites claim that Quan's vortex was dumb, when at the same time other characters could formerly use block infinites on Quan that were easier to execute (by themselves and when it comes to getting them started).
People who understand Quan a little better might say that his skullblast buff, especially in the corner, is a big deal though. It is debatable, that the scaling after skullblast (usually used late in the Corner anyway) or ex runetrap (this would affect Quan's general gameplan) should be increased.
However people forget how bad Quan's footsie tools are. The first trance is not easy to get. Besides his 50/50 does have its flaws. Like the range of B3 making B2 predictable in many cases or like B3 and B2 being fuzzyguardable. I am not saying that his mixups were easy to block, but it is not like they are a touch of death in every situation. Especially as there is a breaker-option too. Fuzzyguarding and only blocking low when the bat approaches will neutralize many mixups.
I do agree that whining on a forum and demanding nerfs is easier than to learn the character. However this is how setup-characters (e.g. hunter predator) should be designed: once you know their setups, they become way easier to play against. However if it would be too easy to recognize one certain setup, the idea of setup characters would become obsolete in general - everyone could play them, everyone could block them without any dedication.
