I tested xtool in Divinity Original Sin 1 EE and 2.
GameMaster.pak[DOS2] => 426MB
Code:
methods:
1) xtool.exe e:precomp:c32mb:t100p:zlib
2) xtool.exe e:precomp:c32mb:t100p:lz4
Result:
Compressed 1 file, 447,157,530 => 447,157,650 bytes. Ratio 100.00%
Compression time: cpu 1.11 sec/real 9.31 sec = 12%. Speed 48.03 mB/s
PAK format