SEN is a non-primary stat, with now very little effect [losing critical defense aspect as of the upcoming launch of the Paradigm Shift update]
The max tier amount for a sub-stat [tertiary stat] is 20, instead of 30 like CHA is.
Given CHA has almost 4x the amount of combat ratings bonus', and it's a non-class / non-primary stat it was given a max-cap of 30 on max tier.
Some info most players may* not know.
SEN provides
0.1 AP [before passive effects + buffs] : 1 SEN or [1AP per 10 SEN]
1 SEN : 1 Critical Rating.
The proposition is simple, increase the Max amount of top-tier tertiary stats for SEN from 20 to 30. For statistical continuity.