Telegraphed attacks, you say? In the old Tera, there were no AoE indicators at all. You either knew to watch for the red eye flash and what attack was coming next in the boss attack rotation or you ate the floor. This was especially important because Tera has animation lock, and you didn't want to be animating an attack when the boss's eyes flashed red.
I would say that Argon Queen in the early days of Tera was as hard as or harder than any raid content in FFXIV. She had a somewhat wonky hitbox too, which made a certain extremely large AoE attack all around her a bit annoying to dodge because most classes had dash skills that stopped when intersecting an enemy hitbox. You had to know the AoE was coming, see the eye flash, turn around 180 degrees, take about 4-5 steps away from the Queen, and then dash/jump/flip away and be out of the AoE range or you were instantly killed. Oh, the lag in Tera made this a fucking pain in the ass sometimes too even if you executed your dodge correctly.
There is still no game where playing a tank felt more rewarding than being a Lancer in Tera. Because the Lancer had an active block with a CD and a meter that ran out, you had to know when to block, you had to block for as short a period as necessary, you had to use your shield swipe on successful block to replenish your block meter, but the block basically negated damage on almost all attacks (one notable exception was that Queen AoE). Also you had to keep attacking when you weren't blocking damage because otherwise you would lose aggro almost instantly, and you were supposed to use your taunt on CD but the long animation meant that if you were animating it at a bad time you couldn't block a big boss attack and you would eat the floor. A good Lancer who knew what he was doing could solo just about any boss in the game, albeit extremely slowly.
