I would agree with some people here that you aren't as bad off as you think you are. You've already listed your offensive weaknesses, and unless you can get somebody like Ryan Braun who's going to contribute in at least 4 (but has a strong change to be a 5-cat stud) I would not let go of Santana at all. The only other way is package Santana or Hamels along with Pence and see if you can't get like a Bedard/Dunn in return, or another above average pitcher that some owner isn't too high on along with a power bat.
I think getting rid of one of your studs actually dips your starters to below average though...I like the overall peripherals of your pitchers, and closer situations generally don't tend to be a problem early on in the season, but dealing one of your stud pitchers + Pence/Bradley for a below tier pitcher and a power bat is really the only move i'd be looking to make in a package, or one for one in separate deals just like you stated. Otherwise, just stick it out for a bit and see what happens.
Thanks for your input with mine.