Plagued mind in 6:1:6 boss

Dtmac98

Was using awakened sentinel on the final boss of 6:1:6, sentinel with plagued mind. Sentinels signature ability is supposed to reduce the effects of power gain based on the number of analysis charges. However in this fight, my sentinel was at max analysis charges, and was still being completely drained of power. Has anyone else had this issue? And if so, is this intentional, a bug, or a mistake? Thanks