Admiral Score:
Screed (57 points, 1188)
Motti ( 52, 1100 mov)
Tarkin (45, 423 mov)
Ozzel (32, 138 mov)
Vader ( 22 points, 421 mov)
Correlation does not necessarily equal causation.
What I noticed when the imp lists were released is that it appeared very much like Screed got the pick of the uniques whilst the others had scraps.
Whereas Rebels tended towards giving Garm the pick of the uniques as the weakest admiral, whilst Rieekan had to make do with leftovers.
Additionally, the poor Rieekan performance was largely influenced by the matchups than an inherent flaw in the admiral.