I don't like having a farm strat and a progression strat. This guild isn't the best at adapting on the fly.
Muln I did some math with Simcraft. With your gear, over the first 40 seconds of the fight, you should be doing 41688 dps without lust and 52376 dps with it.
Lust will boost your dps by almost exactly 25%, for a static DPS boost of about 10k dps over the duration of lust. 10k dps x 40 seconds = a boost of 400,000 damage
Our kargath kill took 6:38 so I did a sim run on your dps over the entire duration of a 6:00 fight without lust and it gave me 27599 dps. That's your average dps over 6 minutes no lust with full raid buffs.
We've already established that Lust boosts your dps by about 25%. If we double your average dps from 100 favor, we get 55198 dps. 25% of that is 13,799.5 dps. 13799.5 dps x 40 seconds = a damage boost of 551,980
With perfect opening lust conditions, you can expect a 400k damage boost. With subpar high favor lust conditions (No saving CD's, no popping pot), you can expect a damage boost of 552k. Lusting during 100 favor is clearly better even in non-perfect conditions. In reality, you would line up your CD's and pop pots bringing the damage differential even higher.
For other classes with ramp-up time, the difference will be even greater.
/math