Seriously?
We can see ships at warp chasing each other in different warp bubbles.
If they shot a torpedo, once it left it's ships warp bubble it would have to obey the rules for real space and need hours to decades to reach it's target.
besides, it can't be safe to activate a warp bubble inside another bubble so of course they also have impulse drives which I always have stipulated.
http://en.memory-alpha.org/wiki/Photon_torpedo