That event is the hardest of all

Much less now with the patch I assume

All is about positionning adds/Vassela not too far one to the other and deal with the adds. And about HER ae, well, the ritual she is doing is during the whole fight. As another hint, I will just tell you that she prefers to remain alone to discuss with the MT so she gets angry if someone else is disturbing the rendez vous for too long

Now it's on you to find a way to make it happen
Trust me if I tell you that even after killing it like 30 times, this is the fight I fear the most, alone or not. And I prefer to do it alone since the window for mistakes is really tight (yet FAR bigger than before patch).
You have all you need to kill her now. Rest of the bosses are easier script wise (though Khas will take you a bit at first).