This is one of those trades that could be great, but could also bite you.
Best case: Batista keeps hitting, Walker posts huge numbers. Worst case: Batista comes down to earth, Walker reemerges as the top DL threat in the league, and the Reds bring in Shaw.
I like Pujols this year. His overall numbers are down a bit, but you have to like the discipline he's showing. He'll be fine. Batista should be solid, too, although his power numbers may slip a bit as the season goes on. He certainly looks more focused than he did in Toronto.
In roto or h2h and points leagues where closers are worth a lot, I'd say you're not getting quite enough return for the risk you're taking on. In leagues where closers are an afterthought, I'd accept this trade in an instant.