jpgames.de Gamescom 2015 interview with Naoki Yoshida

[Daralii]

WoW has way more Slots aviable in WoD:

128 Inventory Slots
223 bank slots
98 Gathering Bank slots (Only for Materials)
80 Transmog Bank slots (only for Weapons and Armor)

Thats a total of 529 spaces. And that for every Character you play to 100.

To be fair, the code they use for the backpack in WoW is a tangled mess that's at least as old as WC3. They have to have a ton of slots to compensate for a technical limitation; from what Yoshida's said in the past, 14's is a server limitation. That can, presumably, be overcome with sufficiently improved infrastructure.