While it IS a good idea to have 12 shards (MORE RARES TO GET =D) I have my doubts about changing the current shards.
Shard of Gratitude is one of the most used shards because it costs 3 of anything! And that's what's so good about it!
Shard of Readiness is one of my favourite cards because, like above, it costs 3 of any element. Making it time, well let's just say it completely bombs my deck.
Overall, if these three shards are put into elements, a lot of decks will be ruined. More than you think.