The forum rules can be found at:viewtopic.php?f=21&t=11242
The FAQ is about as close to rules as you get for GoS.
As far as if there are any rules that govern the decisions the devs make, I do not know. You can try emailing them at email@example.com
I am just another player like you, volunteering my time to help out on the forum. I am not a developer nor am I employed by Sphinx. I only have access to the same information as you, and I too have fallen victim to Spades alt army. I fight daily just to try and stay in the top 30 ranking in Empress lol.
My personal opinion is this: everyone has the same opportunity to create alts and spend as much money on them as they like. While the strategy of team hits by alts, knocking players 10-15 spots in mere minutes doesn't make you feel very good, a guild with good communication and strength could manage the same thing.
There are no rules against it, and within the means of the game, everyone has equal opportunity to achieve exactly what Spade has, whether or not they have the financial ability and time to do it.
I do not like it, but it is part of the game. I do not like that you can multiple of the same heroes in Empress (here's looking at you Hanzo, and Anubis before the nerf), but it's part of the game and player strategy has adapted to find a way to beat it. The same with the alt strategy, eventually players will have a strategy to defeat it.