Yes, buying shards is ridiculously bad value for money, unless you get very lucky - and even if you did get very lucky and pulled a void lego, you'd still have paid a crazy amount for it, enough money to buy several entire top tier games. 

You can definitely try to get your money back from Google / Apple, it might work, though keep in mind that you'll get banned from the game if you do that. Just like a real casino, if you gamble and lose, they're not going to let you try again with the same money. 

Even  on  2x  event  there  is  only  a  1%  chance  to  pull  a  legendary  unfortunately. 

And I would warn against trying to demand a refund. Plarium provides all the information in game in order for you to know exactly what your chances are to pull champions of various rarities. They will refuse to refund - and if you try to do a charge back your account will more than likely be banned.