I just want to say a few things, in my experience, a certain thing has made games a whole lot more fun. Balancing other characters not destroying broken ones. I cannot deny that fl4ks critical build was a very hard hitting glass cannon, but i believe that the fade away nerf was enough to fix him into a functioning character that is not too op. The secondary nerf to his Leave No Trace skill, which was an okay skill that applied itself well into only a few builds, felt unnecessary. An alternative to nerfing a character trait into the ground (and making them a undoubtedly worse) is balancing other character to match the out performing characters. That said, fl4k was only out performing in farming bosses, his nerfed Fade Away made him quite vulnerable in the mob infested battlefields.
All in all, why make a fun trait of a character disappear, why not buff other characters to the point where they match the capabilities of the out performing, and keep everyone happy.