Criminal Sentence 637: Fire Experts or Just Experts?

From something I'm editing (an analysis of the Challenger explosion):

"Even so, in trials by fire experts voiced concerns and created opportunities to reconsider."

When I first read this sentence, I thought perhaps it was discussing "fire experts." If that were the case, the sentence would need a subject--who voiced concerns? A comma will clear up any confusion:

"Even so, in trials by fire, experts voiced concerns and created opportunities to reconsider."

Many times, a comma after a short phrase at the beginning of a sentence is unnecessary:

"In January I visited Australia."

If you want to use a comma, though, that's fine too:

"In January, I visited Australia."  

This kind of comma is often optional (unless you're following an in-house style guide that mandates you use one). I personally like to use a comma most of the time in such cases; others may disagree.

In the "fire expert" sentence, though, I feel a comma is necessary because it helps the reader understand the sentence faster.

P.S. This post is about commas, not clichés, but I do not care for the phrase "trial by fire" in this sentence. Perhaps the writer could have thought of something more original.