I've noticed that if someone joins my party while I'm in a quest then it doesn't count the dailies as completed for me. Is that normal? It just happened again with it not counting the Gorongo kills or the Fang Banshee(s) kills so now I have to run through the dailies all over again and hope no one joins my party so I can complete them.

It did count one before someone joined my party, but after they joined it didn't complete the other two, and it's done this before.

I'm just wondering if anyone else has this happen to them because its frustrating me that I have to keep running through dailies and hope no one joins my party so I can complete them.

That sounds like a bug. Even when someone joins you mid-quest, it should have no effect on any of your Client Orders, let alone ones that require certain kills. All I can suggest is to submit a support ticket, and make sure to set a password on your instance when running your Dailies.