Yes you need both repels on each village to win. I finally managed to do it. Here's my strategy for the last one: THE DESCENT.
Right at the start use infinite earth and build a path from the first village towards the fire power. This is slightly left of the big mountain by the inital village (to the left of the path they take if you do send them instantly). Now that you have this path built send people to the water, fire and second village. You should now get another infinite earth just in time to raise the land around the first village so it doesn't drown. Now while you wait for infinite earth to respawn grab some lava or earth and fill in the small gap between the second village and the ramp to the third. The moment the second village is built send them to the third.
Now the next infinite earth (should be your 3rd of the level) Use this to raise the first village a bit more and build a wall along the left hand path you built. The first village should now handle itself and the two power people be on the way down the path you built to the second. Next infinite earth or two depending on how you are doing use to build up the left hand paths wall again and the wall next to the second village (sea side). By now the water and fire person should almost be at or have reached the second village. Use the next infinite earth to build two small walls next to second village's path heading up the ramp. This is to make sure when you repel water that it doesn't block the path. Use the remaining dirt and later infinite earths to build the wall going up the first straight of the ramp (facing the sea).
It may take a few tries as you have to build the walls just the right height that they block the water but also so you have enough dirt in time to do everything. Your two men should reach the third village as the tsunami is about 50-100metres away and the level will complete.
I hope that helps. It's a pretty long walkthrough for a single challenge because it's very difficult and if you mess up a single step then you can't do the level.