I wouldn't say SW:TOR is a failure so much as a comedy of errors. From the outset it's been one of those things where it makes people go 'Are you serious?". For e.g. Mythic; everyone remembers what they did before working on TOR right? Right? Here's a hint... a failed Warhammer MMO. Also, said Warhammer MMO also used the Hero engine, ooops.
TOR's engine, a heavily modified Hero engine, can't easily be upgraded or fixed. So we have a game where the devs have a hard time just implementing minor fixes and tweaks. Also, this very same engine, doesn't utilize system resources properly.
Now, since the launch of f2p the game does seem to be gaining some strength, but the underlying design problems are STILL there. The removal or fixing of the Hero engine and game performance will be the ultimate decider of if SW:TOR lives or dies.