there is nothing at all wrong with the Hero Engine, it's because EA wanted to push the game out faster they took the engine which wasn't finished and tweaked it for their own purposes, if they waited a little longer until the Engine was complete then launch would of been much more smoothly, while the engine in current use has its flaws due to it being an unfinished product when they started building the game around it, the engine performs very well considering.
SWTOR is in the TOP MMOs categories anyway, the playerbase is still reasonably large and its still generating a good sources of income, if the game was not rushed to release so fast then it could of been in a much better place but i would say not by much, people who play it are the ones who prefer that style of an MMO and will continue to play until they have had enough.