New mutations for Patch 4.10.4:
Undermined
Minesweeper - Groups of Widow Mines and Spider Mines are buried throughout the battlefield.
Void Rifts - Void Rifts periodically appear in random locations and spawn enemy units until destroyed.
This is a tricky one since the path to the Void Rifts will most likely be blocked by invisible mines. The players will need both detection and a fast response to the attack wave and the first Void Rifts. If I recall correctly, the Void Rifts don’t spawn near groups of enemy units, so maybe we can at least be assured that the Rift spots are relatively mine-free. I’d recommend Zeratul here, and Abathur if you tend to be lucky.
Astigmatism
Long Range - Enemy units & structures have increased weapon and vision range.
Short-sighted - Player units and structures have reduced vision range.
We Move Unseen - All enemy units are permanently cloaked.
A pretty sane one after Undermined, since players have a long time to prepare detection before the first wave. After that, it becomes a slightly more annoying version of Malwarfare. Melee or short range commanders like Zagara, Vorazun, Stukov, Han and Horner, and Stetmann are in their element [as long as they prepare detection], but you can’t go wrong with Zeratul, Tychus, or Kerrigan here.
Never Say Die
Barrier - Enemy units gain a temporary shield upon the first time they take damage.
Just Die! - Enemy units are automatically revived upon death.
Life Leech - Enemy units steal life or shields whenever they do damage.
Enemies live longer for this one. They’re harder to kill with barrier, they regen with Life Leech, and they revive with Just Die! The good news is that they’re not actually stronger, so commanders with lots of firepower can still handle this well. Abathur might be slightly tricker since you need more toxic nests to deal with the enemies, but aside from that, any commander can play their usual style.
Medieval Times
Black Death - Some enemy units carry a plague that deals damage over time and spreads to other nearby units. The plague spreads to your units when the enemy unit is killed.
Transmutation - Enemy units have a chance to transform into more powerful units whenever they deal damage.
Not exactly sure how transmutation is “medieval times”, but sounds kinda scary since black death continuously damages your units while the enemies themselves get stronger. Healing will come at a premium here. Vorazun in particular will need a Kerrigan or a Stetmann ally to stay alive because her Dark Templar teleport back to base with Black Death and infect all her workers. So Kerrigan creep or Green Zone is her best best. Of course, Zeratul will still get the job done no matter what, so there’s that too.
Onslaught
Aggressive Deployment - Additional enemy units are periodically deployed onto the battlefield.
Outbreak - Enemy Infested Terrans spawn continuously around the map.
Void Reanimators - Void Reanimators wander the battlefield, bringing your enemies back to life.
Spotting the Reanimators is important for survival. If they make their way into an area that you cleared, or find a trail of infested that burned off during at daybreak, you might find yourself fighting an endless stream of foes. Observers would be a good way to see them coming. Clearing really fast is also a great option. 
commanders need to be careful since there extra waves can sometimes drop in your mineral line if you don’t have any army out.