None of those phrases make sense to me

I'm a native of the U.S. living in Montana.

None of your example sentences make sense to me. Or, more accurately, I wouldn't say anything using any of those phrases. But it's possible you're trying to use a form of "well-rounded."

1. adjective

You describe someone as well-rounded when you are expressing approval of them because they have a personality which is fully developed in all aspects.

2. adjective

If you describe something that is made up of several parts as well-rounded, you mean that the way that the different parts are put together is good, because there is not too much or too little of any one part.

well-rounded in American English

(ˈwɛlˈraʊndɪd ) adjective

1. well-planned for proper balance, "a well-rounded education"

2. showing interest or ability in many fields or showing many facets of personality, "a well-rounded character"

3. fully developed; shapely, "a well-rounded figure"

Webster’s New World College Dictionary, 4th Edition. Copyright © 2010 by Houghton Mifflin Harcourt. All rights reserved.

well-rounded in American English

(ˈwelˈraundɪd) adjective

1. having desirably varied abilities or attainments

2. desirably varied, "a well-rounded curriculum"

3. fully developed; well-balanced

Most material © 2005, 1997, 1991 by Penguin Random House LLC. Modified entries © 2019 by Penguin Random House LLC and HarperCollins Publishers Ltd

well-rounded in British English

adjective (well rounded when postpositive)

1. rounded in shape or well developed, "a well-rounded figure"

2. full, varied, and satisfying, "a well-rounded life"

3. well planned and balanced, "a well-rounded programme"

If this is the case, what would I expect to hear?

I'd expect, and would personally use, the following,

Your writing is well-rounded.

Meaning that you're grasp of grammar, syntax, vocabulary, and writing style is good.

In this context you could say:

Your writing should be better rounded.

But that would sound very odd to me and would take me a bit to work out its context. That might come from my background as a technical writer. In the technical writing world, specificity is important. Therefore, I would expect to hear:

You need to improve your syntax and grammar, but your vocabulary is good.

If what I have just explained doesn't reflect what you are trying to understand, please edit your post to provide more detail about the meaning of the sentences you provided.

None of those phrases make sense to me

I'm a native of the U.S. living in Montana.

None of your example sentences make sense to me. Or, more accurately, I wouldn't say anything using any of those phrases. But it's possible you're trying to use a form of "well-rounded."

1. adjective

You describe someone as well-rounded when you are expressing approval of them because they have a personality which is fully developed in all aspects.

2. adjective

If you describe something that is made up of several parts as well-rounded, you mean that the way that the different parts are put together is good, because there is not too much or too little of any one part.

well-rounded in American English

(ˈwɛlˈraʊndɪd ) adjective

1. well-planned for proper balance, "a well-rounded education"

2. showing interest or ability in many fields or showing many facets of personality, "a well-rounded character"

3. fully developed; shapely, "a well-rounded figure"

Webster’s New World College Dictionary, 4th Edition. Copyright © 2010 by Houghton Mifflin Harcourt. All rights reserved.

well-rounded in American English

(ˈwelˈraundɪd) adjective

1. having desirably varied abilities or attainments

2. desirably varied, "a well-rounded curriculum"

3. fully developed; well-balanced

Most material © 2005, 1997, 1991 by Penguin Random House LLC. Modified entries © 2019 by Penguin Random House LLC and HarperCollins Publishers Ltd

well-rounded in British English

adjective (well rounded when postpositive)

1. rounded in shape or well developed, "a well-rounded figure"

2. full, varied, and satisfying, "a well-rounded life"

3. well planned and balanced, "a well-rounded programme"

If this is the case, what would I expect to hear?

I'd expect, and would personally use, the following,

Your writing is well-rounded.

Meaning that your grasp of grammar, syntax, vocabulary, and writing style is good.

In this context you could say:

Your writing should be better rounded.

But that would sound very odd to me and would take me a bit to work out its context. That might come from my background as a technical writer. In the technical writing world, specificity is important. Therefore, I would expect to hear:

You need to improve your syntax and grammar, but your vocabulary is good.

If what I have just explained doesn't reflect what you are trying to understand, please edit your post to provide more detail about the meaning of the sentences you provided.