If the healer is even halfway decent this should be a non-issue in low level dungeons because everyone can take a couple of hits without any problems. If you are using flash 2 times and then rotating your hits on all the trash, you are fine. Like you said, marking helps a bit if people follow them, and in that case you probably don't need to rotate you hits. Up until 40 PLD is tough to always keep agro especially if people are targeting different mobs and/or doing AOE.