It's not necessarily bad, but the combat shotgun essentially outperforms the double-barrel in pretty much every way. If you're going to be relying on it for close-quarters and you're not very tough (I assume you mean you have low STR, and possibly low END), you really want to be able to kill things quickly. The double-barrel shotgun is powerful, but only having two shots makes it very dicey when facing more than one enemy.
It's not necessarily bad, but the combat shotgun essentially outperforms the double-barrel in pretty much every way. If you're going to be relying on it for close-quarters and you're not very tough (I assume you mean you have low STR, and possibly low END), you really want to be able to kill things quickly. The double-barrel shotgun is powerful, but only having two shots makes it very dicey when facing more than one enemy.