Saving Limit Breaks as a coup de grâce is stupid.

[Tarta]

You are correct, the damage is calculation of the average iLevel of the group. It ignore all de-buffs and buffs. Since it is constant, the weakest DPS of a particular type (melee, range, caster) should always be the one to activate the correct one for the situation.

Incorrect, TA increases the damage taken, not the damage done. Therefore, the LB dmg will be increases.
If you compare Boss HP, LB with TA is actually ~10% more LB dmg than LB without TA.
Always time your LB with TA.
We tested it thoroughly on ThordanEX. (Well, 10 different scenario, those with TA were hitting harder).
Until I find hard evidence that disproves our findings, I'll have to rely on what we found.