That is what DVOA, NEP, and ELO ratings take into consideration to various degrees.
e.g. Everyone knows Seattle was # in rush yards and # in average. But the advance statistics, looking at specific game conditions and opponent, shows the margin is even bigger than the stats say. On the reverse the advanced metrics indicate Seattle is a balanced defense and while the pass defense is very good on an efficiency basis they are only top 3 per play. This balances out (e.g. Cleveland had a great pass defense but bad run defense, but the stats don't mean they are better just the game situations and opponents resulted in higher pass defense effectiveness.) i.e. grain of salt but not irrelevant.
The advanced metrics kind of shoot a hole in the "Seattle had a weak schedule" and are lucky. Sure, it is easy to say, "Seattle got lucky playing Arizona late." OK, but they played a healthy SD team in week 2, got Green Bay healthy week 1, and Denver healthy week 3. They went 2-1 while Irvin and Kam were still recovering from off season hip surgeries and internal strife.
Of course I am sure Seattle was somehow "lucky" against Denver w3 and Green Bay w1, somehow, someway, because it doesn't fit the narrative. Narrative buster? That last 6-8 game spread Seattle let, what 39 points or something? (
EDIT: 39 in 6 games) Only a couple other teams have EVER done that. A lot of teams have had easy stretches and not duplicated that stretch. Someone did the work (google it) and went through every NFL team and took their 6 best defensive games and Seattle's 6 game back-to-back stretch is BETTER than any 6 games ANY team had in 2014 (or top 3, cannot remember, but you get the point). Basically people are saying Seattle is lucky and their opponents suck--but when looking at the BEST performances of other NFL teams Seattle still comes out on top.
For everyone to chew on ELO, NEP and nERD, and DVOA. ELO and DVOA are the best indicators IMO.
ELO: http://fivethirtyeight.com/datalab/...gs-and-playoff-odds-conference-championships/
SEA: 1769 (#1)
NE: 1696 (#2)
NEP & nERD: https://www.numberfire.com/nfl/teams/power-rankings/
TOTAL nERD
SEA: 9.75 (#1)
NE: 9.49 (#2)
OFFENSE
SEA: 138 (#6)
NE: 196 (#2)
OFFENSE--RUSH
SEA: 97 (#1)
NE: 27 (#2)
OFFENSE--PASS
SEA: 61 (#12)
NE: 166 (#2)
DEFENSE
SEA: -54 (#1)
NE: 6 (#6)
DEFENSE--RUSH
SEA: 41 (#4)
NE: -2 (#17)
DEFENSE--PASS
SEA: -20 (#3)
NE: -11 (#4)
DVOA: http://www.footballoutsiders.com/stats/teamdef
TOTAL
SEA: 31.3% (#1)
NE: 22.4% (#4)
OFFENSE
SEA: 16.7% (#5)
NE: 13.6% (#6)
OFFENSE--RUSH
SEA: 29.9% (#1)
NE: -3.6% (#14)
OFFENSE--PASS
SEA: 19.6% (#10)
NE: 35.0% (#5)
DEFENSE
SEA: -16.3% (#1)
NE: -3.4% (#11)
DEFENSE--RUSH
SEA: -25.1% (#2)
NE: -10.4% (#14)
DEFENSE--PASS
SEA: -9.3% (#3)
NE: 2.0% (#12)
Of course none of this secures a Seattle victory. But the Seattle is lucky/overrated/got an easy schedule arguments don't add up.