There is unranked laddering as well in HoTS, so you can just play without caring about points or ladder ranking. It really helps to get you into the swing of it without the ladder anxiety hitting. I am usually on quite a lot, getting my practice on, can always give you a hand/advice.
We build overseers, they just die when you retreat. So you lose 3 overlords and remake, then remorph them. For them to die in the next push, as stimmed marines like a good overseer for breakfast. The whole idea of the patch is to enable us to have a chance of keeping them alive to then save the gas to help get to hive/make blings and other useful units.
It has nothing to do with L2P
Although Scarlets style of not bothering and getting the Mutalisk cloud to a high number is an interesting new tactic.