I believe that this is a big problem for new players, or the players that will inevitably hear news about this game and give it a try.

For us experienced players, it is of little consequence. This said, I believe that any inexperienced player will be very confused with all the HP bars, spells and character models that are presented in team fights.

Who is doing what? Is that a hero, or a creep? If I cast a spell, will I be absolutely sure I'm going to hit the hero I want to hit? What hero is using what spell, from where, and is he hitting me? New players do not know how to distinguish these things, whereas "seasoned" players do.

This problem does not lie in the art direction, as every champion has their own distinct persona and uniqueness. I think that the WC3 glow idea is great, and it would solve all problems with regard to differentiating the champions.

Heroes do not stand out enough against the super cartoony, hyper colored world of LoL.

I'm not sure what you can do about it

Much of this is a brightness/saturation balance issue. Basically, the most important stuff needs to be the brightest and most saturated. Unfortunately, the environment and minions are in some cases the most bright/saturated objects. We are correcting this by making sure that the brightness and saturation of art corresponds to its game relevance -- our art director is doing a pass of all assets in the game and correcting where there are issues.

We are correcting this over the next month. Should be a major update in about 3 weeks that massively improves this.

I'd be one for maybe like a gold lining just around our own heroes name/health plate perhaps?