I've played the demo, and one thing that annoyed me was that for some reason I was unable to stack area of effect spells. That is, if the enemy is in a web, he becomes immune to spells such as silence. If there is someone in an entangle area of effect, he cannot be effected by the more powerful web spell. While this one-area-of-effect-per-square limitation is understandable from a technical standpoint, it would be difficult to see which area of effect spells are active on a square if there are a lot of them, from a players viewpoint, this limitation removes a lot of fun tactical options (Such as using web to prevent casters from leaving a silence area).
Since I was unable to find any mention of this limitation on both the forums, or in the help file, or on the website, I do not know whether this is a design decision (Some AOE combinations may be overpowered or something), or indeed a technical problem, or simply a design oversight (Many AOE spells should logically indeed not stack, but others do).
So, is this something that can be changed?