Beating mobs to 5% life?

[Nooblet]

Alright...i understand the case of not wanting to waste a GDC or whatever...(even though I don't really care about that). Dotting on mobs is also fully understandable and so on and so forth..
what makes no sense to me is switching targets without paying attention to the fact that there is no dot on the first. or not switching back after using your GDC on the second mob. That's just bad playing in my books.

And no, it doesn't result in wiping as has been asked before....but i find it plain annoying if the tank or the healer have to clean up after their DPS.

Perhaps they were making a point that the healer should have had dots on the target, or figure they'd make the healer quit slacking and finish it off... dem lazy healers.

[PArcher]

I will do this occasionally (though not at 5%, usually a bit more) as a DRG, especially when running in a full-relic group. I'll often apply my DoTs and one Thrust combo and suddenly the enemy is at 15-25% hp, not enough to get another combo off (often in a good group I'll only be able to get a True Thrust off before it dies at this point), so I'll switch targets and start applying combos to it. Usually this also involves an assumption that the other DPS will finish the mob off.

There have been some hilarious situations where both DPS (usually double DRG AKs, though it also happens with DRG/BLM there) switch targets at pretty much the same time and DoTs aren't enough to kill it. Everyone just stares at this almost-dead mob for a few seconds after everything else is dead wondering why its still alive, then laughs as it gets nuked.

[Ysarel]

If people are switching early and not going back to kill it if needed, that's bad. But switching early is a good idea, especially with all the DoTs and debuffs you have to maintain in this game. For some classes it might take a few GCDs before they're at a good point in their rotation to switch back, and every job has some incentive to switch before the mob dies.

[Arkista]

Dots........... But on MNK I will do this if It means I will be wasting Opo form, means I can get DK up on the next mob.

[Aetheryn]

As a BLM it's pretty simple - the GCD, along with the cast time of every spell I have that actually does respectable damage, is too long to warrant another cast when the mob could/should/and probably will die before my cast finishes. If the game would actually stop my cast when my target dies, instead of letting me stand there continuing to cast on nothing like an idiot, I'd be more inclined to finish off a mob at very low health. Switching to the next mob is simply more efficient. And in the event that DoT's, or rest of the party, didn't finish the mob off either, I'll throw a Scathe on it and hope the extra damage proc'd.

Also, as others have mentioned, a lot of DPS classes have somewhat rigid rotations. Sometimes you don't want to hit the almost dead mob with a big damage skill, but that's where you're at in your rotation. So you might switch to the next mob at full(er) health at this point. There are a lot of reasons, and people have been doing it since forever.

[TripleH]

Good dps (min max) will do this on purpose. Why? Because it can be super efficient. If theres a 5 pack of mobs (common in WP, sometimes more, even), honestly switching at 10% would be good. The first mob is going to die to 1) dots 2) splash AE damage on the other mobs 3) tank dps (no lol'ing here) or a combination thereof. Instead of spending that extra few seconds on mob #1, you have move frontal uptime on the next mob. Rinse and repeating this can add up.

If you say, so what, its just a few seconds -- then clearly you are not a mix maxer and aren't going to understand.

Some people just want to get through the dungeon.
Some people want to get through the dungeon as efficiently as possible.