Fading to the left immediately means that you don't yet have enough speed and spin on the disc to make it behave as it's supposed to. There is a huge difference between throwing 300 feet on average and 400 feet on average. If you were throwing 400 feet, then that boss would be behaving much differently for you, so I'm guessing you're getting closer to 300 feet, which means a star boss is just too fast and overstable of a disc for you just yet.
As others have said, DX plastic is much less stable than star, especially after you use it for a while and beat it in. If you're looking to step up from your DX Wraith, then you could try a star wraith and see the difference in the stability between DX and star plastic. If you want something that might be a bit similar to your older DX wraith but in star plastic, you would need to step down a little in speed and try something like a star Valkyrie.
Honestly, since you're a newer player, I would recommend working with an Eagle and a TeeBird for a while until you really get the hang of the fairway drivers before moving up to something a bit faster. It will make you a better player overall.