Limit Break

[Anova]

and what is better to do in a boss fight (assuming there aren't too many adds in that fight and that one LB bar is full before initiating the fight):
use it right at the beginning? i noticed a LB doesn't add any aggro
and if it's a fight where you can have more than one bar: wait until more bars are full? or always use it with one bar?

The problem with using a LB early on in a boss fight is that often, you will only have 1 or 2 bars instead of the full 2-3 bars. Often, this last bar appears when the last boss reaches 1/2 hp. So, using a LB later means a stronger attack or a backup in case something goes catastrophic (healer lb). Bosses are also more powerful and have more complicated attack patterns at low hp, so using a LB later helps players to reduce the time spent in the last phase and minimize mistakes that could cause wipes.

The aoe lb from SMN and BLM are used specifically for certain fights where you have to kill many targets quickly (ifrit and garuda fights) or the party will wipe. Consider it a method to simplify the dps check for endgame dungeons. The single-target LBs are as above, just a way to speed a boss through an especially difficult phase. Healer LB is for catastrophic wipes. And nobody ever uses the tank LB.

[Estellios]

The problem with using a LB early on in a boss fight is that often, you will only have 1 or 2 bars instead of the full 2-3 bars. Often, this last bar appears when the last boss reaches 1/2 hp.

This isn't true. You start with 1 bar in a 4 person party and 2 bars in an 8 person party. The extra bar gets added on as soon as you engage the final boss of the dungeon. For primals I don't remember if you start with 2 and get a 3rd upon engaging or just start with 3, but you have 3 bars for those.

[Lemon8or]

This isn't true. You start with 1 bar in a 4 person party and 2 bars in an 8 person party. The extra bar gets added on as soon as you engage the final boss of the dungeon. For primals I don't remember if you start with 2 and get a 3rd upon engaging or just start with 3, but you have 3 bars for those.

Primals you start with 2 and build up to 3 as soon as you enter battle but any progress on LB bar is wiped as soon as you engage the primal. I've never seen a boss that has a last bar appear at lower HP.

[seekerofpower]

Primals you start with 2 and build up to 3 as soon as you enter battle but any progress on LB bar is wiped as soon as you engage the primal. I've never seen a boss that has a last bar appear at lower HP.

Any fight where there are 3 bars, you start with 3 bars. You are correct that the third will always start empty, but the bar is there as soon as the fight starts.

EDIT: Ah, it seems we were agreeing and didn't realize it. Sorry.

[Lemon8or]

Any fight where there are 3 bars, you start with 3 bars. You are correct that the third will always start empty, but the bar is there as soon as the fight starts.

Watch this:
http://www.youtube.com/watch?v=QNSkAuSkyNY
Before the tank engages, it shows 2 bars. After the tank engages, 3 empty bars. I guess I didn't make myself clear. :P But ya you start with 3 bars as soon as the fight starts.