darius:
If I got it right, turtling in AoE means walling in and being scarce (invisible) for a while. In a 3v3 with a strong iron civ, it seems like a good thing to do at first. If you're choson vs tool/bronze civs, you can win even when both of your allies are dead, if they don't get to you until a few mins into iron. Those double-hp long swordsmen are a pain in the axe. If you allies didn't completely die off, like if they ran a few villies into your "fortress", the game can turn very short once you start cranking out your power units.
A good turtling spot, with enough resources inside of an easily defended area for one player to iron and make a large army, could make slow but eventually powerful civs more viable... at least, I think so. How much more viable is hard to tell without trying it a few times.