Is the solution to simply link companion effectiveness to influence ? e.g. rank 1-10 influence companions after 4.02 and rank 50 influence companions before 4.02, with a scale in between where companions receive incremental buffs to health plus stance specific buffs - armor/shield chance for tank stance, crit % and healing output for heal stance and crit % and damage output for dps stance.
This way if you want to run with a powerful companion you increase influence with them and if you don't then keep influence with them low.