I don't think that Boston was "clearly" the better team. Their expected goals were only slightly higher than Vancouver's; it was Thomas playing extremely well that made the difference.
You say Boston won by hard work. Fine. But they were one goal away from being eliminated in round 1, were evenly matched in round 2, outscored in round 3 (winning by one goal), before they outplayed Vancouver in the Finals. They received their fair share of luck throughout their run.
Regardless, I thought Boston was the best team in the East before the playoffs. They had the best goal differential by a fair margin (+16 from Philadelphia, second only to Vancouver). The question for me was whether or not Thomas could sustain his level of play. Which, it turns out, he could.
As for the Tampa/Washington sweep, I watched the series. The teams were pretty evenly matched; Tampa just got some puck luck, and Washington got abysmal goaltending. Goalies have a disproportionately large influence on the outcome of a series. Neuvirth played great for five games, and then poorly for four. If he had mixed it up, it's not unlikely that Washington could've beat Tampa. Small sample sizes. Boston was able to score at the right times when Thomas had his poor series (9 times out of 10 if a team has four games in a series where they score five goals, they'll win). So was Chicago, when Niemi sucked it up through the Finals. The Penguins had Fleury absolutely bail on them during the Washington series, but managed to score 27 goals in 7 games. All of these are examples where due to small sample sizes there were periods of poor goalie play, but the team in question was able to outperform offensively to compensate. Luck.
What I'm saying is that it's easy to look back at something and force a "story line" over it. People say hindsight is 20/20, but it's clearly not. Boston (as a complete unit, including Thomas) was much better than Vancouver over the course of the Finals. But they still ended up in winner-takes-all game 7. Anything can happen in one game, and Boston won. It's revisionism to then turn around and say it was "obvious" why they won.