First, some numbers for comparison:
Going by MealRain's BiS sheet, having the top 6 essences gives you a whole 81 endurance.

Having the top 6 DPS essences with endurance (aka Lycini/Torvan ones) gets you 259 endurance. This is a difference of 178 endurance, or 1780 hp. If we factor in Resonance, it's 187 endurance, or 1870 hp.

So as the thread title asks, is going for full BiS essences worth it in raid? You lose nearly 2k HP doing so, that's over 10% of your total, for a definitely not-10% gain in DPS (correct me if I'm wrong please). As a counter-point, maybe with full raid gear of purples/relics we won't need the extra HP from essences, and you do gain a nice amount of Crit Power with them, which scales very well in raid.

Thoughts/opinions?