Don't get me wrong: grid destruction, or "
slicing", as I call it, is VERY important in TSSSF, for the very reasons you mention. The flip side, though, is that the grid is a resource, and blowing it up constantly will hinder gameplay. I've mentioned slice a few times before in these forums, but it's so important that I'm probably going to dedicate a whole design article to it.
I'm surprised to hear that you feel like you don't have enough slicers in your deck, seeing as how you have all the official cards, like Aria, Wild Fire, Jumpin' Jack, 4 Love Poisons, etc. Check out our
card database to see if there are any fan cards that you would want to add to your deck (especially
Mix Master Magic).
On the subject on grid size, I've noticed that in my games the grid gets nuked at around 20 Pony cards.