I actually don't think the answer here comes from concision. The answer in Sentence Correction is almost never because of concision; however, concise statements do sometimes also remove grammatical problems such as tautology or misuse.

The problem with A and E is that "little" is incorrectly being used to modify "changed", which is used as an adjective (a predicate nominative) here. Think of the sentence, "She is short." You cannot say, "She is little short." You'd have to say, "She is a little short."

B seems to fix our problem, except that by switching from "changed" to "change", we've had an unintended and unjustifiable change in meaning. B says that "the status" is "a little change", which is not what we mean. We mean that the status has not changed very much.

We are left with C and D, which both use "has changed little" correctly. Now, "little" is being used to modify the VERB "has changed." D, however, can be eliminated because, as you say, the verb tense "has been" is wrong. The last century is a particular time in the past, so there's no reason to use past perfect here, because we're not benchmarking a time in the past against something else in the past.