Correct that truth is a defense. But, as I understand it, the defendant does not at any point have a burden of proof in a civil case, even if the plaintiff has made a prima facie case. That's just not how burden of proof works for any tort under US law. The burden is essentially always the plaintiff's by a preponderance of the evidence. Many defendants try to prove truth of their claims so that the plaintiff cannot meet their burden of proof to show falsity. But that doesn't mean they have the burden of proof, in the sense in which it's typically used.
Yes, you're missing a crucial distinction: there are different types of defamation. Defamation of a public figure (which the linked law journal article you provided discusses) places a higher burden on the plaintiff than defamation of a private individual. A public figure must demonstrate the falsity of statements made against him, and must demonstrate malice. The justification is that a public figure is more readily able to defend himself or has others willing to defend him in the court of public opinion.
For defamation of a private individual, the burden of truth remains with the defendant (once the plaintiff establishes a prima facie case). See, e.g., Ellenberger v. Espinosa (1994) 30 Cal.App.4th 943, 953. There are slight variations from state to state, but this is the general rule. (By the way, in case you are wondering, in the legal field, citing a case or statute trumps a law review article or Wikipedia every time.)
As far as I can tell, it doesn't say what you claim it does. There is no mention of burden of proof or prima facile case at all. It merely states that truth is an absolute defense, but that is only the case because it precludes the plaintiff meeting their burden of proof to show falsity.
Since you mention a distinction between private and public indviduals, I suspect you are confusing the issue of burden of proof with the "actual malice" standard, which must be met to establish defamation of a public figure but not a private figure. This is established by Supreme Court precedents Arthur v Sullivan and Getz v Robert Welch Inc, both of which are cited in the law review article I mentioned and both of which maintain falsity as a required element of the offense. (In case you were wondering, Supreme Court precedent trumps Circuit Court precedent in the US, so even if the case said what you claimed it would not be informative about the state of the law of defamation.)
Here's the wikipedia article: http://en.wikipedia.org/wiki/United_States_defamation_law
Here's a random scholarly article on the topic: http://scholarship.law.wm.edu/cgi/viewcontent.cgi?article=22...
I believe they do not support your position.
That being said, I'm not a lawyer and for all I know maybe you are, so perhaps I am failing to understand the issue.