he probably didnt need kabuto IMO.
the first day was actually just a setup for nighttime when zetsus started chaos in the camps by posing as alliance shinobi. the only thing that stopped it was sakura. she captured one alive, and interrogated it enouugh to find out their power and plan, then reported it to HQ who recalled naruto. now this was also playing into obitos hands but left a stronger alliance than if sakura had not been there to cut the assasinations short. if not for her the whole medical division would be in chaos.
second thing he didnt count on was naruto. gedo + chains + kamui was enough to handle bee but naruto proved just too strong for zetsu army/edo jins due to gaining control over kyuubi. with just SM he really wasnt that much of a threat and without madara there the kages would wait evne longer to get involved, possibly too late, thinking they were winning easily when the two jins were being captured. it was a pretty good plan to lure naruto out and demolish the medic division. but alas plot power.
obito was a one man army anyway and with salvos he could walk in, wreck a division, warp out. rinse and repeat.