Content should be challenging to execute... Not challenging to learn

[Chihaya]

Alexander got cleared within 2hr after it came out... you say they followed a guide? There wasn't one.
Did watching video or reading a guide to memorize things give you a free pass to clear t9 or t13? Probably not, you had to actually experience them, survive them and healers to heal through the high damage while dealing with such mechanics.

Remove the mechanics add in a DPS check - that's Bismark Ex that you are so fond of. Dodging a few telegraphs and hitting dragonkillers when the game tells you to - yea... challenge...

[Dualblade]

snip

Alexander Normal is also easier then Coil, the people who cleared it quickly also probably have cleared Coil multiple times, and pretty much are better then most of the player base. Meanwhile there are people who are stuck on the first floor not able to do certain mechanics correctly.

Alexander Savage will be the challenge for even the coil people, so long as the devs have been truthful/are right about player skill levels. And even then expect atleast one group to beat it in less time then they thought.

Also at times the challenge isn't the mechanics themselves so much as having to pay attention to multiple ones at once. Those DKs are so easy...but you let yourself tunnel vision just a little on dps, or healing or dodging that one AoE, you just might miss it.