Breaking these all down:
Both teams are are prime ages for regression, but for vastly different reasons. Most significant regression starts between 26-28, major regression starts at 30. The average age of the teams as currently constructed are remarkably similar. Avs are 28.59 and Dallas is 28.61. But that might be slightly deceiving... Avs are primarily a 27-29 year old team. Taking into consideration players who have early season birthdays (like Mikko turning 27 in Oct), the Avs only have 7 players that fall outside that range. There are 4 above (JMFJ, Manson, Frank, and Cogs) and 3 below (Makar, G, and Byram). Dallas is a much more wildly variable team in age. They have 8 players below 27 and 10 players above 29. Those 10 players above 29 make for a much higher risk of the major individual regression happening... but the Avs being a team where only 3 players are below the typical first stage of regression, make the team as a whole more exposed to a lighter individually, but more widespread amongst regression. Both teams are on the older side in the NHL. Vegas at the average age of 28.26 (half yearish younger than either team) was the oldest team to win the Cup since the 2009 Red Wings.
Dallas has typically been less injured than the Avs, not as much as last season... but the trend is they are a less injured team. Over the last 15 years, Stars have been below average 11/15 years with one year where they lead the league (20-21). Overall, they are roughly in the middle. Avs on the other hand, have been above average 11/15 years while never leading the league. They average out to the 4th most injured team in the league over the last 15 years. It is an odd thing, but the Avs are always one of the most injured teams.
Betting odds are more about money flow and maximising profits than getting it correct. They should really have zero part in team quality evaluation.
Robertson and Heiskanen are legit superstars. Robertson outscored Rantanen last year and has 2 40g seasons under his belt. If Rants is a superstar, Robertson is too. Heiskanen is a near PPG defensemen with elite ability in his own zone. He's a step down from Makar, but still a very clear top 10 defensemen.