Posted this question to Sparton on another thread which talks about scaling stat. Anyway it appear to me that it is based on total and not just base stats.
Mh what makes me doubt is the fact that for example, some abilities (from other sentinel characters) say "based on MAX hp" as if to say "included the talismans contribution", while here i only read "based on DEF" and not "on MAX Def"...
Hope the dev team will enlight us about this