I absolutely guarantee, Ottawa's team defense over the last 3 years was worse than Philly. Only team I'd put below Ottawa in that time frame would be Edmonton.Hell, the Sens weren't even playing an NHL-level system for most of that time.
http://stats.hockeyanalysis.com/teamstats.php?disp=1&db=201316&sit=5v5&sort=GA&sortdir=DESC
8 teams have given up more GA from 2013-14 to 2015-16. Ottawa only gave up 28 more goals than the average team (15th) in 246 games... that's 0.11 goals more per game
I am really not saying Ottawa has been good defensively the last 3 years and I hated that passive defensive system as much as anyone but no need to go hyperbole or get away from facts.
Now what many Sens fans disliked (which was mainly due to that stupid defensive system) is shots against. Even if you look at that, Toronto and Buffalo gave more shots against during those 3 years.
Even in CA60 (Corsi Against per 60 minutes of ice time), 7 teams did worse than the Sens during that period of time
Also, considering the fact that the Sens are a run and gun team (according to NHL players I talked to at least), they like to "trade chances" so it's natural that they give away more chances against than the regular team.
Their CF% (Corsi For percentage = 100* CF / (CF + CA)) is very decent, 16th in the league with 50.1%
Finally, concerning the quality of scoring chances against, we unfortunately can't access the data anymore since WOI is shut down, but IIRC Ottawa was usually around 20th in High Danger Scoring Chances Against, despite being among last for shots against.
Now, before anyone reply with "just watch games", I DO watch games but contrary to many hockey fans, I don't just remember the bad times. They played well in certain stretches, just wildly inconsistent. And if you say Sens goalies make miracles, I'd say yes they are solid but that's NHL goaltending, most teams get high quality goaltending, it's just that Sens fans weren't really used to that before Andy. Look at other NHL regular season games and there is a ton of scoring chances and great saves.