You need to get Wade Miller off waivers right away before someone notices him there. He is a top 20 pitcher with great stuff, great K potential and he always starts the season slowly. He has been rock solid his last 4 or 5 starts and is looking like he's turning it around. Last year, he started off worse than this year and went on to have a 12 game winning streak and tore up the league second half. He is a definite unqualified pickup and he shouldn't be on waivers in the first place.
The other three are also worth consideration. At least in the near term, I would take Escobar second. He has been on a tear lately and is getting ridiculously good run support plus he gets lots of K's. One caution with Escobar is that he is a very very streaky pitcher and will go on tears from time to time but then be absolutely atrocious for a long stretch too. I am not totally convinced that he has put it together but I'd ride him while he's hot and dump him if he has a few stinkers.
Batista has been very good lately but he gets weak run support, and he also is used kind of like Tim Wakefield, shuttling back and forth between the bullpen and rotation, which limits his usefulness on a fantasy team. Clement has the potential to be a stud, but this year has been so inconsistent that I wouldn't really recommend picking him up yet. Monitor his starts and if he puts together a run of good starts, then consider him.
I strongly recommend Miller and adding Escobar is a good idea too. Here is the order I would drop your starters in:
6. Lohse (would not drop him)
I would keep the closers you have because they are all permanent closers while Lyon is a fill-in that will soon lose his job to either BH Kim moving to the closer's role or to a new acquisition.