What’s the point of marines?
Karune: Marines are much more useful than the original StarCraft, mostly because they have more hit points now. Even in mid game, they can be armed with Combat Shields, giving them a whopping 55 hit points. That combined with Stim Pack and Medivac Dropships healing, is quite a formidable force.

Nonetheless, in early game, it is a must to combine them with Marauders, to slow Zealots and force fire Roaches.

Having a diverse group when pushing out early is important. This strategy of course is not the only way to play Terran. There are plenty of other units to play with – including Reaper harassment, standard Tank pushes, offensive bunker pushes, Marine/Hellion pushes, etc.

Are Hellions better to be used against Zerglings and Zealots?
Karune: Hellions are tier 2 and you won’t have them. If you want to push out, using both Marines and Marauders is definitely the way to go, especially since 1:1 at cost in the open, Zealots will tear through a group of Marines if not slowed.

Why not just mass marauders
Karune: Mass Marauders unfortunately would lack the dps that a combo Marauder + Marines group would have. Also Marauders don’t have Stim Pack, which also makes up a great deal of extra dps. The Marauder early game could kite a few Zealots well, but their fire rate is much slower than a Marine.

Are creep tumors burrowed/invisible? How easy are they to remove?
Karune: Creep Tumors are ‘burrowed’ and will need a detector to be able to see them. No need for additional speed bonuses, since Zerg ground units (minus the Drone) will already have speed bonuses on creep. The Creep Tumors now only cost 25 energy from the Queen to create. Using the energy for Creep Tumors though means you aren’t using that energy towards spawning additional larva. Players will have to make a choice in their strategy.