Before this update there weren't really any Store TP pieces for the back. Losing the Attack kinda sucks but if it gets you to a lower-hit tier, go for it!
Could situationally be great for TP as it removes the need to drop haste for sTP, but -15(-30 if you previously TP's with Ame+1/Forager/Cerb+1 etc) atk is quite alot to give up...
The campaign back give store tp +2 so this really is a combination of that and the hoard ring (with negative stats). If you need the haste +1 or accuracy you can get from a ring slot it might be viable.
I'd rather keep the hoard ring and end up with higher overall attack but switch both for WS's - that beind said however, I do not look forward to saving for a white talthum.