The Tampa Bay Rays have played in the less competitive division so far this year.
The AL East has a cumulative record of 212-198 (.517) while the AL West has a cumulative record of 235-186 (.545).
The AL East has a 53-58 (.477) record this year in head-to-head competition against the AL West. The disparity is magnified by the fact the AL West clubs have played 27 games against the Red Sox, 22 games against the Yankees, 24 games against the Rays and 23 against the Blue Jays, but only 15 games so far against the woeful Orioles, who to date are winless* in 15 tries against AL West teams.
The Rays and A's indeed have good clubs but face formidable tasks to advance to the postseason. In race for the second Wild Card slot, the Mariners are seven games up on the Athletics, 10 games up on the Angels and 11 games up on the Rays. In fact the Mariners trail the Astros by only 1-1/2 games, the Yankees by two games and the Red Sox by three games.
FanGraphs currently gives the Mariners an 83.4 percent, the Athletics a 9.4 percent and the Rays a 0.7 percent chance of advancing to the postseason:
https://www.fangraphs.com/standings/playoff-odds
FiveThirtyEight has Seattle at 77 percent, Oakland at 7 percent and Tampa Bay at 12 percent:
https://projects.fivethirtyeight.com/2018-mlb-predictions/
Of course anything can happen with nearly half the season remaining.
* the Orioles lead the Angels 8-1 in the seventh inning as I write.