Working on same storyboard is not a problem. But working on same viewcontroller which creates conflicts on pull/merge is frightening. we can not really avoid that working in same viewcontroller for a large team.
Good thing is, most of the time we can fixed the same viewcontroller conflicts if we understand the xml structure. I never failed to merge these while working in team. Suppose you are working with a viewcontroller. Your view is blank currently. Please ,have a look at the viewcontroller's xml structure from source code option.
Storyboard is xml bounded by document type tag. Everything in the storyboard contains in scene sceneID= tag. scene tag holds every viewcontrollers. Thats the basic.
Now we added a UILabel and a UIButton on the view. Also set the autolayout of the elements. Now it's looks like :
Adding a level/button to viewcontroller added some new code inside the subview tag of the view. Same thing will go for further element addition or any UI changes. Carefully check the tag structure which is really important to fix any conflicts.
Now we add another viewcontroller in the storyboard name Homeviewcontroller. Adding a new viewcontroller means it adds a new scene under scenes tag. Look at this:
At this point, we will change the structure randomly and observe the issues/warnings. We change first viewcontroller label end tag and save the file. Now run it and look at the warning. Error says end tag is not correct which created from line 23. In line 23 , we see a label constrains is set with no end tag. That's the problem. Now we put the end tag and build the project. After setting end tag, we can view the storyboard successfully.
When face any warning of conflicts , please compare with your previous source and changes source. We remove the old/redundant code , keep the new code with proper tag start-end and get things fixed.
[N.B , i will update the answer with some more test cases when get times]