The saucer section can still maintain a warp field for a little while after separation at warp, it could potentially coast quite far out of harms way. Tactical

The saucer section can still maintain a warp field for a little while after separation at warp, it could potentially coast quite far out of harms way. Tactically that would only make sense if the engineering hull could keep an enemy ship entirely occupied, if there was more than one enemy ship engaging then its going to be difficult to keep them all from pursuing the saucer. You are right though, if you did suffer a warp core breach you aren't going anywhere quickly. But in almost all situations help is only one subspace call away.