I don't think the whole concept of a permanent destroying pillars every turn (xcept pulverizer) can be balanceable
So what do you think of trident?
That said, the problem with this as a spell is that there aren't that many pillars to destroy at all, not to mention that earthquake does the job better in virtually every aspect. This isn't even that much more cost effective. Lets look at your new calculation since your old one needed all 6 to be cast to not be strictly worse than Earthquake. Now we'll just look at 4 castings for a reason I'll explain later.
Chain of Water: 2+3+4+5 = 14 Pillar destructions
Earthquake: 3+3+3+3 = 12 Pillar destructions
Here it gets to two more destructions, any less than 4 chain and earthquake is strictly superior. I only used 4 chain because once we get to over 10 pillar destructions, we really have to start asking ourselves what kinds of decks actually possess this many pillars. And even if they 'possess' them then they can't have them out on the field.
Worse still, if you have to play this in the same turn, to see any benefit, you have to wait until turn 12+ (necessarily, assuming a deck of 50% pillars which is about as high as it gets, 7 card hand, and 12 cards drawn, thats when they'll reasonably have 10+ pillars out.). But even with this absurdly ideal example earthquake still outshines for a better quanta efficiency half of the time. And even ignoring that, if you're waiting until turn 12+ to cast this spell they've gotten 10+ turns of quanta generation out of those pillars, which is usually enough quanta to last them the rest of the game, nevermind that you've devoted 6 slots in your deck to denying the opponent quanta that you just kept back for 12+ turns. Or the game is over because they've killed you.
tl;dr: Even with your new calculation, the regular Earthquake spell is superior in almost every conceivable scenario. Because you need to cast this 4 times in a row for this to be in any way shape or form more effective than earthquake, and do it at a time when your opponent has 13+ pillars out, more than most decks even posses entirely.