Are you seriously comparing the amount of time it takes to do a few hand seals to the time it takes to run across many, possibly hundreds of, miles?
Kabuto with SM reflexes and speed can most likely do those seals in less than a second.
Yes it can. Say Kabuto showed up, instead of Sasuke, at the 5 kage summit and decided to summon all the Edos at once to take out Danzo, guess what? He would succeed.
It's not the same as an army because anyone blind can spot a large army, marching to it's target. Way too noticible.
On the other hand, Kabuto slips in quietly, then summons all Edo's at once. That's the difference.
"Yea but how does the jutsu to summon = the person you summon is your power? "
It does if the person you summon is on your side.