It's happening to Boston, as well. They just had an easy schedule to start the season, which gave a false impression of how they are. Boston has done a better job of maintaining a defensive structure to its game. Tampa just doesn't have the defensive personnel to do it anymore. Guys like McD, Coleman, Gourde, etc. were big losses. They were fantastic secondary players.
Having said that, Tampa is sitting on two Cup wins and three straight visits to the finals. No one can take that success away from them. Boston, on the other hand, doesn't really have much to show for this iteration of the team other than a trip to the finals (that they really should have won).