[thaumasiotes]

This is more fair. As yorwba points out elsewhere, though, some pretty large differences between Old Chinese and modern Chinese are masked by the fact that Classical Chinese is always presented with modern spelling[1]. (Other, larger differences are fully apparent.) To be more closely analogous, you'd render "þæt wæs god cyning" as "That was good king" -- and suddenly the gap from "that was good king" to "that was _a_ good king" doesn't look so large.

[1] There are good reasons for this; since Chinese writing bears very little phonetic information, we have only limited knowledge of what Old Chinese sounded like in the first place.

[yorwba]

Applying the same cognate replacement (using Wiktionary as an etymology dictionary) to the full snippet above, I end up with

What. We gar-danes' in yore days

thede kings', thrym frained,

how the athelings ellen framed.

Often Shield Sheafing scathers' threats

many maidens, mead-seats' off-towed

eysed Eorlas. Since erst was

few-shaft found, he that frother bode,

waxed under welkin, worth-minds theed,

othat him each there umsittings'

over whale-road hear should

change yielded, that was good king.