Yes, the story writer will do what he wants, but, I've seen nothing on screen that implies an effect on any that were off planet.
On the contrary, there's plenty of onscreen evidence that the Time War raged far beyond Gallifrey. We were told this from the very start of the new series -- "Rose" established that the Nestene Consciousness had lost its homeworld in the Time War, and "The Unquiet Dead" established that the Gelth had been rendered incorporeal by it. A "webisode" of Sarah Jane's Alien Files
, an online tie-in to The Sarah Jane Adventures
, reveals that the species to which Eve from "The Mad Woman in the Attic" belonged was also wiped out in the Time War. Though most non-time-sensitive species knew the war only as a myth (except for the Sontarans, who were aware of the war but barred from participating as they desired), it was devastating to time-sensitives across the universe.
I envision something like a hotter version of Enterprise
's Temporal Cold War (or like the open temporal war alluded to in "Storm Front") -- time travellers moving throughout history, jockeying for advantage, changing history to make things better for themselves and worse for the enemy, while trying to prevent the enemy from doing the same. It would've been mostly invisible to non-time-sensitives because they wouldn't be aware their history had been changed, but time-sensitives would've been aware of the chaos going on, and would've been drawn into the conflict in their own defense, or become pawns or cannon fodder for the main combatants. Any Time Lords off Gallifrey would've noticed as history changed around them, and activists like Susan and Romana would've surely gotten involved and tried to help. So it's unlikely that they weren't involved. They were probably fighting by the Doctor's side, and he saw them die. After all, if he'd thought they might've escaped, he surely would've gone looking for them. He was certain
his people were all gone; he wouldn't have just assumed that, not if there was any chance they could've sat it out safely.