Don't be "that DPS"

[Februs]

This is not true. As a BLM I will do far lower DPS and have more missed spells if I target the same target as everyone else.

AoE Dps and DoT applications are an exception, and those exceptions do not really matter much for enmity, assuming you are swapping targets strategically.

You said that you have to swap around 50% of the mob's Hp. By that time the Tank should have at least used more than one AoE threat generating move or flat out rotated an enmity strike to the target you are swapping to. Crisis averted. The only problems are when Dps start their rotations on separate targets, or if the target you are swapping to is one that the Tank has not yet landed a hit on. Swapping targets is fine, but you should be conscious of how much hate the tank has on the target you are planning to attack. Carelessly going after the target that has the least threat gen from the tank is irresponsible, especially when there are other mobs with higher enmity in the group that you could have switched to.

You're also confusing personal Dps for party Dps. You're right that keeping your cast alive is the correct decision for maintaining your personal Dps. However, if you are grabbing peripheral hate from the tank by attacking targets that the Tank has yet to establish enmity on, then you are forcing the tank to split their dps (yes, tanks do deal damage). Further, the combined Dps potency of multiple players is higher than any one player can generate on their own, especially if you account for buffs. For example, a Drg's piercing buff from Impulse Drive does absolutely nothing for a Brd if they are attacking a totally different target from the Drg.

Now, if you are simply switching targets strategically to maintain your combo, then that's totally fine. It means you are being conscious of your environment and optimizing your role. However, 2 Dps who start Dps'ing on 2 different targets at the start of a pull are not optimizing the party dps or overall time. They might be optimizing their personal dps, but that doesn't mean they're going any faster.

The only problems I have are slow tanks taking each mob group one at a time (4 pulls from honeycomb to honeycomb I'm looking at your Arboretum).

This is often a Dps issue as well.

When I tank Arboretum, I am all for pulling the whole hallway and skipping the adds, but not all Dps are good enough to make that pull. These days, almost every Dps team I run into thinks they're amazing, but the sad fact is that most of them cannot burn the adds fast enough to avoid Final Stings. Tanks can hold those stings off by using their ultimate defense (Hallowed Ground, Walking Dead, Holmgang), but that defense lasts a maximum of 10 seconds (much less if you are War, and a Drk's Walking Dead can be instantly canceled if the healer doesn't notice it and heals them to full). If the Dps are slow, then there is no point to trying to make a full run.