Well for Entomb, it isn't that hard to spot, since you need to look at your base if you are playing Terran or Zerg, because of Mules and Larvae.
And Entomb can be countered by leaving few units in the mineral line anyway.
In HOTS Custom map, Swarm Hosts were the problem, you could make like 15+ of them, and they would make your life miserable. And what Blizzard did after that... they gave Locust ranged attack, so they can attack air. I can see that strategies that revolves only around Zerglings and Swarm Hosts can be deadly. Not that I complain though, I am a Zerg player, lol. ^^
They could change the look of Locusts a bit, I think that old ones were a lot better.
EDIT: HOLY SHIT! I just watched the Unit Video again. Look at the end of the Video, the final Zerg vs. Terran battle. Seems like Swarm Hosts have the upgrade to produce 4 Locusts instead of 2 at the time. That is actually brutal upgrade, and you need just few of them(3-4), to have a lot of small units in the late game. And now that Locusts are ranged, seems like that Swarm Host with Brood Lords, Infestors and Vipers will be sick as fuck!
Can't wait to see the pro matches with these.