Eh... What?
"Dominated" is exactly the right word.
First of all -- the Soviets: On the rare occasions when Gretzky played against them in best-on-bests (those in his prime years between 1981 and 1991), here's how he did:
9GP: 3G + 14A = 17PTS (weirdly, he didn't score against them in one game in '91, but anyway...)
So, when the Soviet Union team was at its best (1980s), Gretzky only got 16 points in 8 games against them, in best-on-best tournaments (at Canada Cup). I haven't got the Soviet players' stats to hand vs. Canada, but it would be interesting to compare...
Then, to your point about "Mickey Mouse clubs": In Gretzky's salad-days in Edmonton, here's how he did in regular season against the top teams in the NHL (top between 1979-80 and 1987-88):
vs. Montreal
28GP: 17G + 35A = 52PTS
vs. Philadelphia
27GP: 27G + 32A = 59PTS
vs. Boston
27GP: 12G + 28A = 40PTS
vs. Calgary
62GP: 47G + 92A = 133PTS
vs. Buffalo
29GP: 15G + 35A = 50PTS
So, let's see... Against the NHL's top 5 teams during those nine years (excl. Edmonton, obviously), Gretzky put up a grand total of: 173GP: 118G + 222A = 340PTS
If you project this pace to an 80-game season, it's: 55G + 103A = 158PTS -- which is more than any other player in history had ever scored in a season -- and this is an average for 9 years. So, domination again. However, in reality he probably would have put up better numbers than that if he'd been playing these teams regularly. As the playoffs show, when he played such teams (Philly, Boston) more often, he did better...
Now, what about playoffs? How did Gretzky, with Edmonton, do in the third and fourth rounds only of the playoffs, when those weaker and more offensive teams like Winnipeg and L.A. were already dispensed with? Let's see:
vs. third and fourth round in playoffs:
50GP: 30G + 71A = 101PTS
If you project this pace to an 80-game season, it's: 48G + 114A = 162 PTS -- which, again, is more than anybody before him (or any player in history except Mario twice) had scored, ever. And that's in the championship rounds of the playoffs, when most players' scoring stats go down by as much as 50%.
So, in conclusion, Gretzky dominated the Soviets, dominated the best NHL teams, and dominated against the toughest playoff competition. Better luck next time!