well, a 2 man team wouldnt necessarily be immune to genjutsu, remember in one of narutos first encounters with itachi, he not only could use his sharingan eyes but also the sharingan symbol on his ring. Also i firmly believe that a genjutsu user such as itachi has the skill to lock multiple people in his genjutsu, its just after the first person falls prey the others focus on snapping them out of it(mainly because i think it would be boring if he simply genju'd a 2 man team and then stabbed them). Also as far as bee, when dealing with a powerful genjutsu, once again such as itachi's the 8 tails isnt a guaranteed remedy. Remember in the recent episode, the 8 tails was shaking him to try and snap him out of it but he was out cold until samehada jumped in, and from the look of what it did, i dont think bee broke free of it because of a chakra transfer from the sword, i think it happened because of the sword slashing its spines into his hand, after all inflicting pain on the body is just as effective a release as a burst of chakra.