Yup. Unfortunately, all the previous franchise heroes/villians will have no reactions to her. Blizzard REALLY should go back and add a few lines to each of those heroes reflecting later added heroes. (The original heroes group, for instance, have NO specific responsed/kill voices/ect for heroes added past Anub'Arak. Arthas does not say anything to Sylvannas/Jaina, nor says anything when he kills Sylvannas/Jaina. Tyrande/Malfurion/Illidan, nothing to say to Kael'Thas.)
Wheres the !@#$ing Blizzard Quality at? Oh, wait...
- - - Updated - - -
If she's an assassin, she will do quite a bit of damage. She may be more of a sustain auto assassin though, with her ult being her only burst ability.
Tracer is one of the squishiest heroes in Overwatch though, so she will likely have Li-Ming lvl health, or lower.