Lots of people aren't getting this so I'll explain:

In any trash pull with 4+ enemies everyone is going to be doing more DPS (SMN and BLM especially but that's beside the point), because four enemies is generally where AoE attacks both do more damage and are worth the TP/MP vs single target attacks (there's a few exceptions, arm of the destroyer, for instance, is only better than bootshine at 5+ and only really better TP wise at 6+, assuming you're getting your positional on bootshine).

The greater the number of enemies, the greater everyone's DPS will be.

Lets use Rockbreaker as an example. I can, as a monk, either Snap Punch, Demolish, or Rockbreaker. Rock Breaker is 130 potency on every enemy, Demolish is 350 potency on one once all ticks hit, and snap punch is 180 on one enemy.

At 5 enemies, Rockbreaker's effective potency is 650. Meaning, for that GCD, I'm doing almost twice as much as if I used Demolish and got every tick in and a little over three and a half times as much as if I used Snap Punch. Even bootshine crits are only 225 potency while Arm of the Destroyer's potency on 5 enemies is 250.

And that's not including Elixir Field or Howling Fist or the fact that these gaps widen when you consider the damage buff from GL or any damage buffs of any kind, and monks aren't even particularly good AoE, but in an AoE situation I can easily grab another couple hundred DPS compared to single target. A BLM or a SMN can get much more than that.

Meanwhile, in an AoE rotation, swapping targets for the couple non-AoEs I need to toss in reduces my DPS--and every other melee DPS--by nothing. I maintain that same DPS if I swap from weakest to strongest for dropping twin snakes and true strike, and the same goes for any other class.

But if I don't swap, my DPS drops marginally due to my AoEs becoming weaker, and dots not being allowed to finish out. A SMN or BLM's DPS drops by considerably more.

WHAT ALL THIS MEANS in TL;DR format is that not swapping targets is a relatively hefty drop in overall party/raid DPS.

Does it increase the pressure on the tank and healer? A little bit, sure, but if a tank/healer can't handle that extra pressure, the tank shouldn't be multipulling and AoE rotations should never even enter into the picture and none of this matters, including the opening post.

Not swapping targets means you're sub-optimal. It doesn't mean you're bad or anything, and it's fine. It generally only matters on trash, and is only going to speed up a dungeon by a couple of minutes tops, so it's not a big deal. . .

HOWEVER, all the people arguing that swapping targets is wrong or a DPS loss or is, jfc, making the dungeon take longer just to pad someone else's parse? You're wrong. Not even a little wrong. A lot wrong. Not even understandably wrong because the fact that AoEing does more damage is incredibly basic common sense stuff, so it should equally be common sense that maintaining AoE rotations for as long as possible is ALSO more DPS.