I don't think it's harsh. I was actually feeling a tiny bit sad in her death scene when she was trying to will herself to be brave... and then PSYCH! "Nope, she's not dead after all - okay, she's sorta dead, but just suspended between one moment of death and being REALLY dead, and oh, look, is that a new TARDIS in the shape of a 1950s diner? SEE YA!"
I don't like being manipulated like that. If they're going to kill her off, make it permanent. Make it something the audience cares about, and don't cheapen it. Sara Kingdom didn't get to come back. Neither did Katarina, Adric, or other characters who died unfairly. They got around Peri's death by saying it was Timelord manipulation of some sort (don't recall the details). But she didn't stay on the show; she was given a happily-ever-after ending married to Brian Blessed's character (King somebody-or-other). And then she was really written out.
I know Adric returned a couple of times after his death, but he wasn't really there - both times were hallucinations, once when the Master was trying to influence Tegan and Nyssa, and the other when the Doctor was regenerating and obviously still feeling guilty about Adric's death. He wasn't magically zapped back to life or given many improbable chances at cheating death.