I just finished Esseles and for a first flashpoint I think they did a good job
I did not investigate this game before it got released for the fact that I love to be surprised.
The Esseles Flashpoint was long enough. It took me a good hour to finish it. The rewards some enemies dropped were really helpfull and the dialogs were interesting.
If I remember correctly you will eventually fight 3 human enemies and 2 droids as for bosses (the droids belong to the bonus quest). Each one was stronger then the boss before so you had a good build up.
The only small downpart of the entire flashpoint was the Sith you had to fight at the end (Vokk?). He had a crapload of HP but was weaker in strenght then the second droid we had to fight. If the devs would add a little bit of strenght to him, it would be perfect!
All taken into consideration, I think they did a great job