I can't speak for DotA, but isn't LoL's business model to continuously add new characters? This constant change never lets the true balance of the game be discovered the way it is with SC:BW. Players constantly need to adapt to new characters and modified game elements. It's not necessarily bad, but it's very different than leaving a game alone for a long time. For example, chess never got any patches, but new techniques and strategies developed for ages.