Gai could probably solo..........
I say Hinata and Gai win with mid difficulty. Without Hinata, Gai could solo with mid-high difficulty. Not much to say here, Neji and Lee aren't close to surpassing their sensei based on feats. Even if Lee could use the same number of gates as Gai, which he can't, Gai would still have the speed, power and stamina advantage because his body is more durable and fit for the forbidden technique. Neji could hold his own by rotating but Gai is too fast for him and eventually Neji will be overpowered or out sped.