I feel Dallas has quite a lot untapped potential, so I wouldn't write them off.
In the regular season, the teams leading goal scorers were, in order,
Robertson, Johnston, Duchene, Hintz, Marchment and Dadonov, all putting up at least 20 goals.
Currently Robertson, Duchene, Marchment and Dadonov have 2 goals between them in the postseason, so it's not even really that their depth is struggling, their best scorers through most of the season have been shooting blanks. (Which likely says a lot about the quality of the opponents.) Rantanen was on a barely 20 goal pace after the trade to Dallas.
Based on regular season numbers, you could actually argue that Granlund-Hintz-Rantanen IS their depth scoring
It would actually be somewhat anomalous if this continues, you would expect their regular season top guys to start looking like their actual top guys at some point, and if that happens while Granlund-Hintz-Rantanen continue ripping it up and Oettinger plays as good as he has, I don't see Oilers having much of a chance.