In general, you'll probably only be able to manipulate two opponents if you outclass the crap out of them. In early testing from when the latest version of Manipulate went live, I found that Manipulating one difficult opponent awarded more experience than two of something that I could manage to pull it off on anyway. So finding a more difficult opponent is probably your best bet as far as Empathy experience goes. But if you're looking to improve your chances of getting that second creature, you could try increasing the stats that impact Concentration and see if that helps. Try it with Mental Focus and Tranquility in effect on top of Gift of Life, if you're not already. Maybe that'll be enough to put you over the edge a little sooner.

Thanks,
-Biomancer Karthor