sortByTen

//CC-BY Nik Ska, 2014

var sel = app.project.selection; //selected
var used = []; //these were used

app.beginUndoGroup("Precomping as hell");

var precompFolder = app.project.items.addFolder("Precomps");


for(var c = 1; c <= Math.ceil(sel.length/10); c++){
    //creating comps
    var newComp = app.project.items.addComp("Precomp " + c, sel[0].width, sel[0].height, sel[0].pixelAspect, sel[0].duration, sel[0].frameRate);
    newComp.parentFolder = precompFolder;

    var count = 1;

    while(count <= 10){
      var r = Math.floor(Math.random()*sel.length); //random num
      if(!used.isThere(r)){ //if this number hasn't been used
        newComp.layers.add(sel[r]); //add the corresponding comp to precomp
        used.push(r); //mark it as used
        count++; 
      }
    }
}

app.endUndoGroup();


Array.prototype.isThere = function(el){
    for(var i = 0; i<this.length; i++){
        if(this[i] === el) return true
    }
    return false
}

1. Select N comps, where N is divisible by 10
2. Script creates N/10 precomps
3. Each precomp contains 10 random unique selected comps.