Dorian thought he would be reaped in the last two years because he thinks his sister was reaped as punishment for their parents' rebelliousness. He is not surprised when it happens this time. He does, however, have a surprise for the Capitol viewers, when he flips the whole crowd off and gets dragged off stage screaming obscenities.
Arsenia doesn't expect to be reaped...but then, she's also not terribly surprised, either. Having been born sick, she was expected to die in infancy but stubbornly held on into her teenage years, mostly a recluse. Without proper medicine being provided in District 12, it's nothing short of a miracle she's lasted this long. She figures this was bound to happen eventually. She's still scared, of course, but gets through her reaping to the best of her abilities, mortified at the attention Dorian's causing.
District 12
Dorian River
Arsenia Magnus