Swihart was hitting .231/.310/.385 as of this morning but his DFA is likely more a function of the Sox trying to do something - anything - to get the pitching staff back on track. León can't hit a lick but his game-calling skills and his defense are superior, so he'll get the call when Christian Vázquez isn't catching.
The 27-year-old Swihart was once a top prospect but has never fulfilled his potential. Whether that is on him or on a Red Sox organization that never seemed to want to commit to him behind the dish is unclear, but what's done is done. You have to figure that his reputation and that potential will get him a shot with another team, whether that occurs via trade or if he is released and signs elsewhere.