Looks interesting overall, but I’ll note that the only branch that a Castweaver would likely take has something which will not be usable in most arena matches (constant interrupts and CC ensure that Sheilun’s Gift remains unused or even a liability, unfortunately.) I would make this to a timed ability or somehow tied to having used TFT 3-4 times rather than being dependent on SG.
I would also ask for Blizzard to review my list of Castweaver suggestions, particularly the one about removing Soothing Mist from the GCD, which would help us immensely in PvP and not (IMO) hurt PvE: