My Fleet and I, The Knights Templar, did the Infected on VA Saturday. We had a little trouble with Rebecca too but we settled on using one of the corners and just blasted her and spammed powers at her and widdled her down. I'd say she was at about 5% when she wiped all but one of us and it was really tense but our last member beat her and he had about 1% health when he did lol. We loved how ground 2.0 changed her.
I returned to Infected with the Jade Empire folks tonight, and we took down Rebecca! At last, I got to see the end of the mission!
We used the cover shield strategy mentioned above. The three jumpers finished on the lower left platform, and the two middle people joined us at that point. We took down the reactor and raised a cover shield while Rebecca was speaking. Whenever someone had the blue circle, they hit behind the shield and Rebecca would just wait until she switched the circle target. Rinse, repeat. It worked like a charm.
The best way I have found to kill her is to have everyone on one of the corner platforms to buff each other and to avoid taking fire from all the borg spawns.
1) Have your Engineers put up cover shields to protect your team from the spawning borg from the center and closest platforms and to use to break line of sight with her.
2) Once she finishes her speech, use team buffs and watch for her targeting recticle (the blue circle) once a teammate is targeted get him to hide and break line of sight with her either behind a cover shield or the transformer (watch out for the Plasma).
* If the targeted player hide quick enough, she seems to be confused and doesn't move to attack or fire and just stays still. While your targeted player is hiding he can revive and still buff the team as they continue to fire on her. Once the target recticle is gone that player can continue the attack until the next player is targeted then they have to follow the same procedure.
We used this method tonight, worked like a charm. 3 tacs, 1 sci, 1 engineer.