i don't think you'll get looper back if you put him on waivers. try to switch up your claim.
generally, anyone who IS the closer on any team will be picked up. you just want to have as many solid closers on your team as you can... unless having too many compromises the # of starters or bench position playrs that you have, shoot for as many as possible. it can never hurt to have too many saves, plus closers are good for the occasional win (not to mention implosions)... so having 4 closers means you might get ~130 saves and ~12-15 wins between them all. sure, you can hope for 3 closers with 40+ saves to get that ~130... but it's a more solid bet for 4 to do that.
i love closers on the DL too.. if they can come back, hey, they're free for now. i've been nabbing alfonseca, putting him on the DL, then nabbing another player. if he comes back as the cubs closer, woohoo ,i've got a closer for a .500+ team that has had a good deal of close games. if he isn't one, oh well, free pickup.
don't drop looper. he might save 30 this year, in fact, he probably will if he doesn't implode/lose the closer's role.