If your daughter cannot even balance on her own at this point then yes, I would bring this up to your pedi. Before children walk they are able to balance themselves standing up. My daughter was a late walker as well-it took her until almost 16 months, but pediatricians usually start to take note at 18 months. She might be fine, and just a late bloomer, but by 18 months it is something you would want to check out just to make sure there are no other underlying conditions, you know?
Around that age is when my daughter was hitting too. I would take her hands and hold them in mine, make sure she was looking at me and say "No, we don't hit. Its not nice." In my *mom means business kiddo* voice ;). If its in response to frustration tell her its ok to be mad-you understand why she's mad even, but that she cant hit you/bite you for it. Its not going to catch on over night, but with consistency it should.
And to mention something that someone else did-how is her speech? If she's having trouble communicating, have you tried toddler/infant sign language? Toddlers love to immitate, so its not to late to try it. That gives small toddlers who cant communicate verbally the chance to, and can relieve some frustration for them.