It sounds callous to say, but it's only natural that as the War of the Ring heats up in The Two Towers, some of the characters in these books are going to suffer, big time. What makes this unavoidable suffering even worse is that Sauron actively enjoys making people hurt. He's not just trying to conquer the world as a means to an end. He really enjoys the whole mess of war. When Pippin picks up the palantír and looks into Sauron's fiery eye, Sauron laughs at Pippin's pain. And through the One Ring, Sauron continues to cloud Frodo's mind and to twist his thoughts every minute of every day. Sauron is not just a killer; he is also a torturer. And as the trilogy continues, we see more and more evidence of this hateful love of suffering in all of his choices.
Éowyn has suffered a great deal, but she's so cold and unapproachable that we can't, as readers, sympathize with her suffering.
The more Frodo suffers, Sam must go stronger to compensate. While it may appear that Frodo is Ring-bearer, carrying the Ring is actually a two-hobbit job.