I'm not sure that shows are tracked outside of Nielson sets.
While it's conceivable that DVR and cable boxes report viewings, that's not something readily advertised by cable companies.
Because they don't want advertisers having access to the actual DVR usage of "8 minute delays" to just skip commercials. The cable providers generate as much revenue as networks, maybe more, from advertising sales.
Now shows accessed via Netflix, Hulu and in AoS's case ABC direct are tabbed up pretty accurately. Networks are moving to online services and APPS because they don't want to have to dicker with cable providers.
Also ABC is gonna do Exactly what Momma Disney wants. Momma Disney wants the availability of AoS as a cross platform marketing tool. It's a slick weekly ad for the Marvel Properties, those are currently a cash cow. Even the weak movies have turned a profit. The show doesn't need to win giant ratings or even it's time slot to be considered useful and profitable.
Arrow's success and Flash coming is pressure on Disney to stay relevant in the super hero TV platform. They can be happy beating WB at the box office; for now. It's gonna be a game of chicken between WB and Disney for a couple of years. Both will take some risks in the next few years. Disney spent more in the acquisition of Marvel and has been successful in capitalizing on that investment. WB has let DC sorta sit for too long and they know it, they don't need to recoup any upfront costs but they know that the Super Hero Bubble could pass them by. WB wins in animation and TV, so far. Disney is killing at the box office. Both sides want to win the other arena. Ratings aren't what they were once especially in these shared worlds where billions of dollars are on the line at the end.
It's a good time to like funny books.