@Zedd:
The crux of the matter is not whether or not there is a genre of games similar to DOTA (or whether or not MMORPG is/was a genre). It's whether or not DOTA merits trademark protection.

The specific term MMORPG never merited trademark protection because it was born as a generic term that tried to describe a nascent genre of games. It doesn't matter that the genre was in it's infancy. Trying to trademark it would be akin to trademarking "text editor" back when computing was in it's infancy; you can't trademark something that is just a generic description of the product.

DOTA is not a generic term. It's a game name (or mod name, whatever), and not a generic description of the genre. The fact a whole genre sprung from games like it does not make "DOTA" any less deserving of trademark protection (and the fact it was not the first such game makes any claim that the name "DOTA" describes a genre even less valid).

On the other hand, the terms "MOBA" and "ARTS" would not merit trademark protection simply because they ARE generic descriptions of the genre :)