There is one annoying thing about teleport spell which bothers me since the very beginning and i do not know whether it is a bug ... When you have an army there is always a leader (the first one in stack) and only he/she can teleport entire army. If you have an army led, let's say, a dragon (the most powerful unit) and you have a hero there too, there is no way this hero can teleport dragon anyway ... If you select dragon and a hero then the spell cannot not activated. Hence, you can only teleport units that are lower in ranking then the caster ...