Hey now,
I had exactly this trouble using a CC phoenix 25 in a 3-D foamy, drove me crazy! I thought it was the esc (nope), reciever (nope) maybe even the motor (nope). I finaly discovered it was the battery (naw, couldn't be!). I'd charge it up, according to my volt meter it was fine, but never the less it'd cut off early.
When I used my whatt meter I found out the pack voltage under load was dropping to below cutoff level quickly. From what you're saying it does sound like you're overdriving the battery either because it's old, abused, or just too small for the set up.
Before you smash the esc try a bigger/newer battery pack. I bet you fifty cents this is you trouble.
RobII