How to play gladiator efficiently?

[Raldo]

I agree with many others' comments, though I'll add a few more, since it's unclear what specific problem people have with you.

• Don't stand in the "bad".
Many hard-hitting moves are telegraphed by an orange indicator on the ground. You should try to avoid those. Hopefully that's obvious, but I'll mention it just to be safe.

• Don't move a lot while you're tanking.
Several people mentioned "face things away from the group", but it's equally important to mention "please try to rotate/move the monsters as little as possible". Obviously, you'll still need to dodge the bad stuff mentioned above, but always try to return to your original position. Other jobs have moves that work better when striking monsters from the back or sides, and it's difficult to hit those directions if they monsters are spinning/moving.

• Dungeon speed.
I suspect this may be the actual reason people might complain about you. People hate it when dungeons run slower than needed.
Since you're doing low-level dungeons, people may be bitching if you're pulling small groups of monsters. Once you've leveled past a dungeon and you've gotten used to the dungeon layout, it becomes obvious that certain groups of monsters are so weak that you could easily pull multiple groups at a time (the first two groups of monsters in Sastasha are a good example). So many people have run all these dungeons so much that it seems obvious to them, but for newer players it's definitely not obvious at all.

With that said, there isn't really anything you can do about this until you are comfortable with each dungeon.

At least 80% of the time, the monsters are aggroing ME and NOT THEM. Yet despite my efforts, other players get mad.

What am I missing here? Like I said, I'm already using flash. Exactly how many times do I need to spam FLASH in order to COMPLETELY SECURE aggro?

"80% of the time" is not NEARLY sufficient to be a tank; you should be aiming for ~99%. Also, this may seem contradictory, but they may be complaining if you're flashing too much. Once you have a decent enmity lead, you should be actually hitting the monsters, not just flashing endlessly. This will be gear dependent, but you should only need to flash 1~3 times to get solid threat.

Also worth mentioning that flash trumps shield lob; you shouldn't be using shield lob if you're in melee range.