Ok some advise.

1. Be aware of patrols. If needed, mark target 1, 2, 3 and so on or with X and such. It's nice with a mark if you need someone in group doing something special, like off tanking with a titan/yellow carb.
2. Pull with shield or tomahawk.
3. Flash the mob (if you're a war/mrd and you have no BLM or TAM in group, use overpower aswell).
4. Always face mobs AWAY from your group so they wont have to move from cones and other AoE.
5. Keep your eyes on the enmity meters.
6. Pick the right gear. Gear with MRD/WAR/GLA/PAL on, try and avoid lancer gear or DoW gear in general, except on rings and such as you level. The gear designed for the tank classes have much higher defense than the one also desiged for lancer.