Jiraiya is awesome for his debuffs, but he's not worth having due to his mystery isn't prompt. I mean possibly for a f2p team in ranked he may be viable, but others will sure out-shadow him. Oro bring a decent balance of attack and some light tankiness(not over bearing) with his passive to rez he can be annoying, but like his sannin counter-part jariaya there are far better choices currently. Tsunade really is the only curent sannin viable in my opinion on your team; They are all viable for ranked( Don't expect to be able to complete with premium members though)

GNW Kankuro I believe is phenominal for f2p, he might not have the best chases, but his ability to poison & ignite an entire enemy team is a win!