Well since this is an issue isolated to you : Test another launcher, test another java, test everything considering your PC like HDD, RAM ...
Get the version from git and overwrite the local files ...
Are you seriously asking Whovian41110 to perform HDD and RAM tests for missing textures? Unless you have undisclosed history where this has been the case, this ask seems totally irrelevant, kind-of-a slap in the face, and a goose-chase waste of time.
@Whovian41110
If your problem is strictly missing textures, then it's either the pack or the launcher [or both]. If you have other gameplay issues, it may be Java. Unless I've missed something official with FtB packs, they still don't play well with Java8. I'd recommend Java7 final release [you'll need to sign up with Oracle to download]. Since you mention most of the missing textures are vanilla...try loading up vanilla through the launcher and see if you get the same results. If so, backup saves, delete everything, then re-download and install new launcher. Test vanilla again. If pass, re-download pack until no missing textures.