I agree that OWL shouldn't have big changes like this in mid-season, but with viewership dropping like it did, I don't think they had a choice.
I think for OWL, long term it will be a good thing. Teams will know exactly how to build their roster, not running into situation like NYXl benching 2 players like Sabaeyobe and Pine for most of the season.
What it won't do is prevent stagnant meta, I'm sure that a new 2-2-2 meta will develop that will played by all teams, all the time like it has been the case for the past 2 years of OWL. Whether it was Dive for 3 stage in season 1 or GOATS for 3 stage in season 2, in both case people got bored of watching the same meta being played 90% of the time.
As for ranked, as a gold player, GOATS was never an issue, it was barely played, and when it was, the team simply lacked the coordination to make it work so it wasn't really dominant.
I think the benefit will be that we will always get the basis for a good comp with 2-2-2 with people actually wanting to play the roles, rather than filling as something they either don't really want to, or simply not be good at.
You'll still have bad comps with a Hog and D'va as tanks for example, but it's probably better than having 5 dps and 1 healer.