The only real similarity between X-COM and D:OS: Both are turnbased games, after this point there a many huge differences, I would say. X-COM has mission based combat scenarios while D:OS is open world with prebuilt scernarios. In X-COM you have pretty much endless amount of enemies/missions to grind experience and loot, only special encounters are limited. D:OS has a definite amount of enemies. Just to mention the main differences combat wise. I really don't think you can say: X-COM and D:OS are the same. Or would you also say X-COM and FF VII are the same?
Randomizing encounters coud only happen, if every fight would take place in a special combat instance.
The reason why there are only a few walking around enemies, because other wise sneaking at the enemies would be often quite impossible, if you want to prepare your team for a fight.
Also the finished D:OS will have a Tactician mode with more difficult and respeced battles. More or different enemies with different skill load outs for example.
