That's a very broad question. There are lots of factors that go into play; the quality of the kibble, the advertised ingredients, the activity level of the dog, etc.
If you would just feel more comfortable with the answer "yes", then I have heard a LOT of rave reviews about Solid Gold's Seameal. I used to use it before jumping in on the RAW diet and it seemed to serve it's purpose.
Supposedly the kibble is "complete and balanced" so you shouldnt' NEED vitamins unless it looks like your dog needs them or is acting like it. I think Solid Gold is the brand that admits that the vitamins and minerals lose most of their potency in the cooking process so they say you need to add them in separately. And Blue Buffalo says this too, but cold forms theirs so they keep all their potency and then adds it to the bag. I guess.
Hard to say... my dogs don't get vitamins in addition to their kibble and their coats are shiny and they are healthy. Not sure if giving them additional vitamins helps or not. I don't think it would hurt them. Try giving it to them for awhile and see how it affects them; i.e. shiny coat, etc.
Depending on the quality of dog food you buy, you shouldn't "need" any additional supplements. However, it's ALWAYS a good idea to add fish oil capsules. I also have used "Show Stopper" by Animal Naturals for skin and coat and it's absolutely amazing. It's a little pricey, but definately worth it i you have coat issues, itching, and shedding. I swear by it.