MK is Ike's best partner in my opinion.
MK offers great stage control with his tornado, and Ike can easily fair/upair people as they pop out of it for low percent kills or general damage.
Platforms to indeed help, because of both characters generally being good with them and platforms helping Ike to get high enough to punish people who pop up out of MK's moves.
MK's Dthrow can sometimes pop them low enough for a fsmash, but both dthrow and up throw can both combo into an upair if you predict their DI well enough. His quick forward and back throws can also quickly get opponents into the range of Ike's moves. If the Ike can react quickly enough to situations, he can get a lot of ridiculous kills off of MK's general ridiculousness.
As for saving Ike, it's incredibly important to note that you have to hit him from behind while he's doing Aether or you're likely to get sucked in and die with him. If the Ike isn't going to make it then he has to reverse aether away from the stage so MK has time to get over and hit him. Also, it helps if the Ike stalls in the air with counter to give the MK partner enough time to get over to him.
It's really an amazing team.