Going by TCDecks' Tier decks history of 2013 (we won't argue the accuracy of TCDecks' ability to predict the overall metagame):
GP Denver 2013 was January 5-6.
January: 1st - Blade Control
February: 1st - Blade Control
March: 3rd - Blade Control
April: 1st - Blade Control
May: 4th - Blade Control
June: 11th - Blade Control, 13th - Patriot (we see a dip in Blade Control here)
July: 3rd - Deathblade, 9th - Patriot, 14th - Blade Control
August: 14th - Patriot, 17th - Deathblade, 18th - Blade Control (another bad month for Stoneblade)
September: 4th - Patriot, 15th - Deathblade, 24th - Blade Control
October: 4th - Patriot, 18th - Blade Control, 23rd - Deathblade
November: 2nd - Patriot, 4th - Blade Control, 17th - Deathblade
http://www.tcdecks.net/tierdecks.php...&format=Legacy
As you can see, with the exceptions of June and August, we have always had a UWx Stoneblade deck in the tier 1. Post-Denver was actually Blade Control's best months.
As expected with TNN, we are seeing Blade Control starting to make a comeback (Patriot is still doing well) and I wouldn't be surprised to see Deathblade start coming back as well.
So, while TNN obviously does make the UW/x SFM decks better, they were hardly Tier 2 before TNN was around.
So now you're getting into a different conversation from if streaming coverage is representative of the metagame of a tournament (which I believe it isn't).
If you want to talk about why you should care about the non-tier 1 meta, there's a plethora of arguments about that, especially in a format as broad as Legacy. You can very easily face 8 different decks in 8 different rounds. The power level difference between Tier 1 and Tier 1.5/2 decks in Legacy is very small. What you'll face in your Swiss rounds is likely to be very different from what you'll face in a T8. Local metagames (US vs Europe, East coast vs West coast, for example) matter greatly in Legacy. Etc, etc, etc.