I think the meta has changed drastically enough that double sentinel is more viable now than no sentinel, depending on the map. I also do believe teams have had more time to learn and create ideas around the newer sentinels (Deadlock/Vyse) and as such, their pickrates and winrates will both rise.
In addition to this, as much as I think there's a ton of talent in tier 2, Split 3 isn't really the best source of data when it comes to data and that kinda thing. Teams don't have the top analysts and coaches in the world; rather they're trying to innovate themselves, and obviously the average quality of comps and ideas is going to be a tad lower than that of tier 1