I think this must be a response to a few things which have changed since Titan has been in development:
– The subscription payment model fell out of favour with just about everybody as the online games market reached a saturation point. Publishers discovered that charging players for a game often doesn’t make quite as much money as giving the game away for free and charging players for silly hats instead.
– Blizzard is rushing an online TCG to market to hopefully gain some headway over the other major entries into this growing genre.
– Every MMO which was thought to have a chance to replicate WoW’s success failed to do so and World of Warcraft has continued to be mind-blowingly profitable despite an extremely competitive market.
First of all, Titan must have at least some kind of framework of core gameplay mechanics in place, mainly because I’ve heard whispers from people who got to play it internally that what exists of the game is really really good. I think “large design and technology changes” is probably about updating the overall frame of the game to work with whatever business model they have now decided to pursue. Let’s just hope that whatever it is, it’s still viable in 2016.
Taking people off the project is just a matter of opportunity cost, and I’m sure that the chance to reallocate resources was a major reason for the shift. Hearthstone is a game for which getting to market in time might be the difference between moderate success and LoL-sized success. It’s also entirely possible that the next WoW expansion is behind schedule, and you know they want to keep the eight million players of that game happy. We’ve heard the Blues talk on numerous occasions about how they can’t hire new people fast enough…
But mainly, I think this new MMO was intended to pick up the slack as WoW started to lose market share, and when this didn’t happen as quickly as expected, suddenly it didn’t seem prudent to have so many resources dedicated to a product which may well cannibalise an existing success.