Part of the problem is that quite a few attack strategies get hard countered by a single buff on pests. Knights with 80/50 evasion and/or accuracy debuffs lose out when a boss effectively has 200% base accuracy, Knights with attack debuffs get countered if/when a boss has +100% (or more) attack power, some bosses are resistant to solar burst damage, etc.

Meanwhile it seems that there aren't too many bosses with strong defensive buffs so stacking as much crit damage along with capping crit rate tends to be the best way to go. Even if the boss does have strong defenses they're usually built with a drawback (high defense only if the incoming attack isn't of a certain type, high defense for X rounds then effectively zero defense for the rest of the battle) so crit stacking still wins out in the end.