You might want to take a moment to examine yourself. I just read a post blaming the healer and DPS for your inability to perform your role as a tank. I know it is hard being a tank, especially when you are starting out and while some of the grievances you aired are legitimate, this "everyone else is to blame" attitude will not make things any easier for you. You will always have areas where you can improve. Always.
It might seem like every DPS you encounter in PUGS is impatient, and it is true to some extent, and understandable to an extent. They waited 15+ minutes to get in the door, and they want to get it done so they can fit in their next 15+ wait and dungeon. If you find that your DPS are pulling ahead or throwing out AoE before your flash, think about how you are contributing to the pacing of the dungeon.
If you are in a pre-Rage of Halone duty, you are also in a pre-Stoneskin/Eye for an Eye dungeon, so there is absolutely no reason why you need to be pausing between pulls (exception: you or healer’s MP is critically low. But if it is your MP that is low, think about how to better manage it next time, if your healer’s MP is low, think about if you stood in too much red or didn’t use CDs). Unless your DPS are using sprint to get ahead of you, you should be beating them to the next pack.
When you get to that pack, take a look at how they are positioned. If they are already clustered, I use Overpower on them without a Tomahawk, and I have seen PLDs use Flash this same way before as well with great results. Usually, however, there will be at least one mob further away than the others. Shield Lob the furthest one, while bee-lining for the rest. Flash the rest while the far one approaches, and flash again while facing the whole pack away from the party as desired. Note how there was no "waiting" involved in my description here? A tank doesn't wait passively for monsters to come to them, a tank is controlling the pack from the second they approach it onward.
If you don't mark, the mob you Shield Lob is usually considered first target by your DPS. That said, DPS will AoE when it is advantageous to do so. That is their job. Rotate your targets. Get a feel for how much hate needs to be built on the primary target before you safely start building hate on the other targets. If you find that you spend more time on one mob, flash before switching targets.
Lastly, I would advise against the “you pulled it you tank it” shtick. Try diplomacy first. “Please allow me to pull the mobs.” A good amount of the time the DPS are pulling on accident because they are eager and the tank is sluggish, so starting out hostile is not the way to go. If you start to see them sprint ahead or they argue, maaaaybe you can start letting them tank things but you can and will probably be kicked at that point. This is because when you “let the deeps tank” and the healer tries to save the day, the healer will get aggro, and you all will wipe. While the deeps is wrong for pulling ahead, you certainly aren’t right by not doing your job.
This is especially true if you do this for packs that you were able to pull yourself but lost aggro on. In my whole tanking career I’ve done “you pulled you tank” once, and that healer was clearly trolling and not performing their role correctly. If you find yourself doing this as often as it sounds, you need to look at what you are doing.