Although quite powerful in his time, the 16th century Russian czar Ivan the Terrible seems to us as a remote and barely visible historical figure.

* to us as a remote and barely visible historical figure
* to us to be as a remote and barely visible figure of history
* to us a remote and barely visible figure of history
* to us a remote and barely visible historical figure
* to us to be a remote and barely visible historical figure

both C and D omit 'as' whereas "seems as" and"seems to be" both are acceptable idiomatic expressions.
need some clarification...

i didn't look it from idiomatic terms. In fact yesterday i read somewhere that before nailing a q for idiomatic reasons try to find at least one other cause for eliminating that answer choice.

Whenever we see a form of the verb to be(or any other verb of being) be sure that the 2 sides (across that word) are parallel. For eg words such as appear, seem, become, smell ,feel.

Now using this strategy in the above question

Although quite powerful in his time, the 16th century Russian czar Ivan the Terrible seems us as a remote and barely visible historical figure

* to us as a remote and barely visible historical figure --- Russian czar is as a remote and barely visible historical figure it seems like something as a remote and barely historical figure.
* to us to be as a remote and barely visible figure of history--------again it seems that czar is as a remote ........ and not is a remote figure
* to us a remote and barely visible figure of history----czar is a remote.......OK but figure of history is wordy
* to us a remote and barely visible historical figure-------czar is a remote and barely visible historical figure OK SEEMS GOOD
* to us to be a remote and barely visible historical figure----czar is to be a remote and barely visible historical figure..again meaning is getting changed

Hence IMO D