Starting with career goals allowed (exc PPGA) per 80 games.
Sedin 45
Nieuwendyk 51
Thornton 53
Modano 53
Turgeon 56
Lindros 60
Damphousse 61
Sundin 63
Crosby 66
Messier 68
Oates 71
Obviously this is unfair to Messier as he played such a significant chunk of his career in a high-scoring era relative to the others (especially Crosby and Sedin).
So limiting it to the 12 seasons when nine of the 11 played a significant part of their careers and were established as first liners (1993 to 2004):
Nieuwendyk 48
Modano 54
Turgeon 54
Damphousse 55
Thornton 59
Sundin 62
Messier 62
Lindros 62
Oates 68
Ice time and quality of goalies and other teammates likely explain part of this, but I think the data create at least a preliminary case that Oates was not that good defensively, and that Nieuwendyk, Modano, Turgeon, and Damphousse were.
I think there's some value in the goals against data, but there's a fair amount of context that needs to be considered.
Let's look at Modano and Turgeon. They might be the best and worst defensive player on this list, respectively. But they're on the ice for the same number of goals against per game. Let's see if we can figure out why.
Let's look at 1998 to 2004. Those are the first years we have actual ice time data. Modano was on the ice for 281 ES goals against, Turgeon 232. Modano played 520 games, Turgeon 465. So that's 43 ES GA per 80 games for Modano, and 40 for Turgeon. (It's a bit lower than your list since you went back to 1993 - the higher scoring years are excluded).
So that suggests they're in the same ballpark, with Turgeon somewhat ahead - right? Not really. We know from the official NHL icetime stats that Modano played 11,175 ES min, Turgeon played 8,071 minutes. So their personal GAA's were 1.51 for Modano, and 1.72 for Turgeon. So Modano's GAA is about 14% lower, and we haven't even talked about matchups yet. And suggesting that Turgeon's defensive responsibilities were anywhere close to Turgeon's is obviously wrong. (Not that there's a perfect correlation between PK duties and defensive duties at ES, but it's worth noting that Turgeon played 9 seconds per game on the PK during this period; Modano played 2:28 per game, nearly as much as players like Lehtinen, Maltby, Draper, etc).
The response may be this covers most of Modano's prime, and Turgeon was past his prime at this point. They're nearly the same age, but Modano clearly peaked later. But this still features Turgeon's only two seasons in the top five in points per game, so it's not like he was washed up during this entire period. Besides, there's no evidence that Turgeon was good defensively during his earlier offensive prime (in 1993 he was on the ice for 84 ES goals against - tied for 4th worst among forwards that year, on a team that was league average in terms of goals against).
The observation I made when we had this discussion last year is Turgeon's GA numbers are dragged down by his 2000 season, when he was on the ice for 19 ES goals in 759 minutes. Either we can conclude that Turgeon suddenly became a Clarke/Datsyuk calibre defensive forward for one year only, and nobody noticed - or maybe he was the beneficiary of playing heavy ice time with Chris Pronger at his absolute peak.