Re: Mystic Snake's questions
Your arguments regarding blink/leap is true, but this is due to the fact that these skills move your hero away from MS's range. Void's Backtrack can at least dodge the damage from snake, though I am not sure wether it dodges the mana steal. Would appreciate it if someone could enlighten us on that topic.
Cycloning yourself will help, due to the fact that a cycloned unit is invulnerable. An astral imprisoned unit is completely removed from the map for it's duration, so this would also dodge MS. TP'ing with BoT or scroll will not help you dodge the snake while channeling the teleportation, but when you have teleported you are (hopefully), again, out of snake's range.
Damage type is magical. Will be reduced by your hero's magic resistance.
And yes, blade fury gives you magic immunity, and thus you will dodge it.