I think it's true though. If you get a bunch of competitive players together, and they figure out that that can get more return for X amount of effort, they will generally gravitate in that direction. It's just natural tendency.
In MK9, Kenshi actually took a lot of work to be able to win at a top level as a Kenshi-only main -- he was only relatively easier in certain matchups. That's why by the end of MK9, there were a ton of pocket Kenshis. Not mains, but people who would pull Kenshi out to win a MU in Top 8. Basically they did whatever gave them more return without having to expend the full effort of mastering all of Kenshi's top-character MUs.
Likewise in Injustice, when it was announced that Flash and Wonder Woman were "broke", a lot of players picked them up early. But when they saw how much work it was to get wins at a high level, about 95% of those players dropped those two characters for new ones. Likewise with the people that played Catwoman, and Killer Frost.
Put another way -- I don't think you'll see a Grr with Grundy. If you look at how much work Tyrant has to do just to keep his character competitive with the top, it's pretty scary and that's why it's natural that he's the only player so far who seems to be making a dent in the top cast with Grundy.
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