Here are a few showing that, when speaking about history, it is normal to reserve terms like "first rate" for the truly exceptional:
"Jonathan Edwards, a very stern Calvinist, is one of the few first-rate geniuses America has to boast in theology."
"For excepting Philae, which belongs as much to Egypt as to Ethiopia, Abu Simbel is the only temple which can be ranked among first rate products of Egyptian genius."
"Pericles likewise is responsible for the epoch-making splendour of Attic art in his time, for had he not so fully appreciated and given such free scope to the genius of Pheidias, Athens would hardly have witnessed the raising of the Parthenon and other glorious structures, and Attic art could not have boasted a legion of first-rate sculptors of whom Alcamenes, Agoracritus and Paeonius are only the chief names."
Plus, all the actual definitions given there are vague enough to not actually solve the ambiguity.
It was the person I'm replying to who used "first-rate" actually. I don't think there's a big difference in meaning between the two.
Usage examples show nuance in the meaning of a word that are not captured in the definition.
“By the early years of King Charles I's reign, these four groups had been renamed to a numerical sequence. The royal ships were now graded as first rank, the great ships as second rank, the middling ships as third rank, and the small ships as fourth rank. Soon afterwards, the structure was again modified, with the term rank now being replaced by rate, and the former small ships now being sub-divided into fourth, fifth and sixth rates” --wikipedia
When figuring out the definition for a term used, the best source is the context it is used. In this case, Hypatia is the benchmark given for what qualifies as "first rank."
You can then argue the author is misusing that term, but that's a different argument that the article doesn't make.
That said, the “of all time” version also doesn’t sound right.
"Who are the first-rate/first rank musicians of $YEAR" does not seem to me like it could be answered with "there were none in that year".