While you can amass a large battlefield, they do not have much in the stats department, making them weak in combat
It requires setup, and the opponent isnt going to be sacrificing essential permanents right away, but this is the right spell when the right situation is on the board
Splashing changeling cards like Bloodline Pretender, Gladewalker Ritualist, and Littjara Glade-Warden is also a solid option
In fact, it was die rolling itself that led us to the decision to make over half the set Eternal legal
Yes on that as well
A creature with Protection from a quality, let's say a colour for simplicity, can't be targeted by spells and abilities of that colour (like Shroud, that's regardless of who controls them)