Some firing/impact sounds are very 'soft' indeed and
plop plop plop-style at times. Those two examples could do with a bit more 'boom' but Pillager already makes good noise when the projectile hits.
Seems hard to find a compromise between loud/epic/impressive audio and unnerving noise when the sounds of dozen/hundreds units blend together.
Especially shrill/high-pitched sounds get annoying very fast.
Some units (artillery!) can be alive & shooting for a loooong time.
It also has to sound good at different zoom levels.
For some units I am glad that they error on the 'too soft' side.
Related: "worst sound in zK":
http://test.zero-k.info/Forum/Thread/6665The sounds in zK are (mostly/attempted to) credited to their orginal sources, which is nice.
[Spoiler]