I can't imagine how they're going to create a real combat system with manipulatable voxels. Minecraft is fun for a time but once you figure out the AI it's very simple to ruin a mob's ability to path. My favorite escape plan is to run to a wall, bust through it and close the other side. Will be nuts if they give mobs the ability to destroy voxels to chase you.
Well, you can only build inside your own claim in this game, so you would be unable to do that tactic anywhere else. In your own claim, you should be able to build traps ala Terraria to keep the mobs at bay. While I have no doubt that there will be mobs that break voxels, I doubt they will be able to break your creations, so I expect to see lots of pulling mobs into volcano or spike traps on their properties for easy exp/loot.
Since we are only able to destroy voxels outside of our own claim and not place them back, there is no reason "normal" mob AI shouldn't work just fine, where you can dig into a hole and try to get away from mobs that way, but if you can destroy something, so can they (outside of the claims). Could potentially build claims together to form a gauntlet for the mobs. If you have to run from mobs and try to hide on someone elses property (assuming this game will turn into a "survival"ish sort of game, where you will need a house), you will not be able to enter without permission. So technically the only safe spot in the entire zone would be your own claim.
Edit: Possible example with storybricks.
You are digging in a mountain, a gnoll hears/spots you within aggro range. It can not get to you due to geometry, it paths to the gnoll camp to get a pickaxe. Once it gets it, it is now more dangerous (weapon) and it remembers its last target, paths back to your last location. If you are still there, it starts coming towards you. If not, there is now a gnoll with the ability to come after miners in the world.