Just because something is fast doesn't mean it doesn't require strategy. A good SC player on fastest is going to kill anyone on a slower setting because he'll be even better. You have zero advantage over a better player if it's slower, you are not a "genius strategy master" that is only unable to use this skill due to the game being too fast.
The same goes for Demigod, slow does not equal more strategic and fast does not equal less strategic.
With that said, given the map sizes compared to dota, I don't really think much more demigod movement speed is needed. I don't think the movement speed is what makes the game feel "too slow." I have played against people who push really early, and this makes the game feel fast enough. I think most players are generally just not good enough to play the game to where it feels fast enough (myself included.) Think of some of the games though where a team did a really strong push that killed someone early, took a flag, and then took towers down very quickly. This kind of initiative is required to make the game more exciting. When neither team manages to do this, it feels slow because you'll have both sides just whack-a-moling flags back and forth while trying to neutral creep. You'll often even have, at low levels, demigods from both sides creeping in the same spot and not engaging each other, simply because it's not worth the mana and not worth wasting time that could otherwise be spent creeping.