I love your platinum pave, am personally not so much of a fan of the rubedo but I understand that was a gift and it depends on your taste. I do think that platinum as a metal has a more understated look, not so shiny but many, including me, love that. You will find the same with antiques, they will not sparkle as much (sometimes, as it is not always the case), however, me personally, hate dirty metal and stones and actually clean my antiques thoroughly as well. Most the time I use dishsoap and a toothbrush although you can actually microwave diamond and platinum in water mixed with dishsoap, it works similarly as an ultrasonic. I do have an ultrasonic myself but find that unless they are really good, heavy duty machines, they do not work as effectively as hand cleaning with toothbrush and dishsoap which will help even really dirty antique jewelry. Many times the lack of sparkle (brilliance) in diamonds comes from them being disgustingly dirty (sorry) and not so much the cut, or not only the cut itself. Diamonds should be cleaned on a daily basis when possible but at least every three to four days, as after a mere three day period the light return is reduced by as much as 40 %. This is a huge difference and even the best cut diamonds will suffer greatly from it. Diamonds should be maintained and so should jewelry. We wash our clothes, clean our shoes, jewelry is much the same. Nothing is as disappointing as dirty diamond jewelry, they look tacky to be honest. You were probably sold a piece without first cleaning it, perhaps due to the holiday rush but it should have never happened. I think that now after cleaning it looks great but it is up to you, you can just keep the rubedo and get a different diamond piece. The price is typical of Tiffany and the like, you pay for the name, some are willing to and some are not, it is a personal choice what you spend on. I have mostly non branded pieces but have one branded piece as well. I do have to say that oftentimes good brands will warrant quality for many years to come but you can get superb workmanship from no brands too and sometimes the name does not guarantee quality as to workmanship.
I hope to one day pair the arrow with more zeigfeld items like the tassel necklace or the pearls... even if it isn't from Tiffany. The diamond ones are part of the Jazz collection though so if they get confused just specify the collection.