Noun, Na-adjective (keiyodoshi), Noun which may take the genitive case particle 'no', Taru adjective, Adverb taking the 'to' particle
galaxy of able persons; collection of intellectuals
Yojijukugo (four character compound)
これだけまあ、多士済済の人材が一堂に集まったもんだよな。Not bad―not bad at all. This is quite a gathering of talent to have under one roof.
Also written 多士済済【たしせいせい】