It was +10% increase to one's Defense stat, not 10% bonus mitigation -- same as to base Foresight. Even on a tank, that was worth still worth less than 5% mitigation by i130. On anyone else or at lower ilvl, it was worth considerably less.
Which is why when 2.0 Warrior complained that they had no mitigation and people pointed at Foresight's Defense increase and said, "There! Your mitigation!" anyone who knew what it amounted to knew to point and laugh in turn.
Note that a majority of player buffs functioned in that way at that time. Fey Glow increased the Spell Speed stat, not spell recast time; Fey Light increased the Skill Speed stat, not weaponskill recast time. Only enemy-damage-suppressing effects not directly attached to players (Sacred Soil; RoH and DK, though even they weren't 1-to-1) and debuffs scaled (Foe Requiem initially reducing Elemental Resistances, and Slashing, Blunt, and Piercing Resistance Down, again not quite 1-to-1; Trick Attack) as we'd now assume.
Because the mistake wasn't JUST in that single GCD after it was too late to correct; the mistakes were in each time you made decisions that left you no time to refresh your DoT at the correct time.RE DoT to 60 seconds: The current situation is you have several bad options. That's not choice. All the options are a DPS loss, and...the same DPS loss of one tick's worth of DoT damage. It doesn't matter if you refresh the DoT 3 seconds early or 3 seconds after it fell off.
Which is why your hyper-narrow definition of "mistake" makes no functional sense.
You aren't forced to make one of many bad choices. You're encouraged to not have made the successive mistakes that brought you there in the first place. You weren't forced into a position you'd have to salvage; knowing the fight, unless the tank gets extraordinarily unlucky against AA crits on an especially tank-pounding fight, you'd have had multiple chances not to put yourself into that bind in the first place.
Which is still a mistake. That you repeatedly neglected to check your footing and therefore fell off the bridge doesn't make it any less a mistake.The true "average" is the average of all of that together, which probably means NOT noticing when your DoTs fall off all the time, or even somewhat often.
And that is not something to fool-proof jobs out of.
Near-proportionately higher ceilings for higher difficulty as perceived by the average player (or each job having similarly high ceilings) is a sign of good balance, since most players are not perfect and we want to widen the number of competitive choices available to players in practice, yes.
But, to ignore most all the decisions prior to the point at which their rewards/punishment become obvious would provide only a very narrow slice of what comprises difficulty for the average player. Your framework would quickly become incompatible with player findings.