We’ve gone through this feedback and discussed the issue. We’re now planning on making archmage gems, town portal gems, and Tusker Island gems stackable for the May event.
Players who wish to continue using these gems as death items will need to make sure that they either leave them unstacked, or keep a number of separate stacks in their inventory.
Thanks to all for your feedback on this topic!
Thanks to Ron Jenkins for letting us know about this!