Explain how you get 600 diamonds a day.
Arena - 300
Plundering - ~120
Mines - ~150
Monthly diamond card - 120 (optional but is only 2 bucks so, easy to afford)
This alone is 690/day
But there are more:
Roughly once per month there is an update where they give you 200
Roughly once per month there is a double arena rewards event for 3 days, so another 300*3 = 900
Daily Login rewards = 500 per month
These give you an extra 1600 per month, which is an average of 53 per day.
So 690+53 = an average of 743 per day
Now, let's say you don't buy the monthly card at all, only get 150 per day in the arena and can only dig 2 mines at the same time, then you can get an average of 400 per day.
And I'm not taking into account the raid records, each one you beat is 100 diamonds.
And in regards to the stones, also factor in the fact that unless toon is awakened and at least 5 stars all 3 stones cannot be equipped so for those players who may have a Sylphi awakened but 3 star because Lilith is too greedy to put her or Goram in the shops, they can never equip all 3 stones on her until she reaches 5 star which would mean buying her to 5 star.
Sure, but there are a toon of good heroes in the shops to use the stones: Malrath, Octo, Avior, etc, etc. Are you worried that you will fill all your good heroes with stones and still have leftover stones? It will take years to equip everyone... Good slots to use the stones is something you will not be short of.
No matter what case you make for the Tower and its rune rewards in reality is took absolutely no thought on the part of Lilith when adding the Rune feature.The game was not lacking additional stats with the fact that there is already equip, enchant, train and forge. They could have put in any other feature and it would have been more useful than Runestones.
Maybe, that is debatable. I think the runestones are a good idea (not the fact that if you pay a lot you can get gaia stones faster than everyone, but that is another matter). I would prefer a different feature that added something more to the gameplay and would keep us entertained, sure, but those are not mutually exclusive, why not have both?
The tower is supposed to be such a feature and, to be honest, I don't really think it is that great, it adds a bit of strategy but the novelty will wear very fast. I think it is better than the previous tower though but I wish it was something with a more permanent challenge.