Thinking through a rough example of deciding whether to use Inspire Recklessness for a boss fight.
Suppose we're fighting Velah with 2 healers, 5 THF guys, and 5 TWF guys (no WF here, because they're immune to the Recklessness penalty). For a regular battle, the healers basically alternate casting Mass Heal according to the hitpoints of the squishiest melee guy (whoever gets too low hp first, which will probably be the same person over and over).
Using Inspire Recklessness gives 5% more DPS to THF and 2.7% to TWF, for 3.85% more average. Assume Velah did not take a feat for stronger crits and is only at 19-20/x2, she'll average one crit threat per swipe, and there's a 10% chance it gets through the reduced Fortification. So the average rate of an actual crit is one per 10 swipes, which doesn't sound too bad (although sometimes there'll be more). These crits change the healer behavior in two ways:
1. When a crit happens, they must react to it and fix that guy, either by spot-healing him or accelerating the next mass heal. (The spot heal costs 45 or 90, because the two healers might double up. The masses are 60).
2. The mass heals need to be performed faster, because the safe hp threshold players can be allowed to sink down to has been increased.
Tossing some vague numbers onto there, the 10% of swipes with a crit lead to +67 spellpoints used. What's the effect of needing to keep players above the level where a single crit is fatal? Say the lower-hp melee guys are 500 hp and a regular hit is 110, we need a mass heal every 3 swipes, or every 2 if crits are possible. So that there
is a 50% increase to the rate of healer mana expenditure, which appears to dwarf the 3.85% they'll save by the fight ending about 10 seconds sooner.
That looks quite bad, although the result can be improved if the lowest-hp melee guys turn off Recklessness, leaving only the higher-hp ones at risk of being critted. But that's problematic for the healers to keep track of, because then the characters driving the mass timing (by being most at risk of death) will have a drastically higher hp bar than those who are actually safer.