Besides Blitz, you have two options:
Stay slightly spread out. The only real danger there is the Galio/Amumu ults because they can trap you, keeping you in MF/Fiddle's ult. Their AoE's are really not that large. If your team stays slightly spread out, they will end up wasting their ults on a tank + 1 instead of your entire team. Of course, to do that, you need guys who can enter combat quickly once ults are popped. Janna, Ez, etc basically anyone with some speed and/or a flash. Also, tenacity, so you aren't stuck there forever if you are caught.
Or split push. This'll be a kite fest and/or tower sit while someone who can BD well safely (Yi, TF, etc) push another lane. This could be hard if their tanks get fed because Galio and Amumu will start diving pretty hard, making the 4v5 dangerous.