The problem with class quests isn't that people don't pay attention, it's that they're implemented/tuned badly.

For example the Marauder class quests have absolutely nothing about tanking.

Gladiator class quest you can get through a whole fight with just 1 Flash, after that it's always better to use Riot Blade (dps over enmity) to clear the quest.

In the later tanking class quests, it's always a quick death for you if you try to tank all the enemies. So for a newbie who believes the classes quests, he will always be "tanking" only single target, with Riot Blade (or basically the highest dps attack) as his main attack---i.e. the worst tank one can possibly hope for.

Conjurer quests you're just spamming stone, and the only one where you can try to heal NPCs, you get pounced on by water sprites and the NPCs ignore you. In the end you gotta Stone the sprites if you even want to stay alive. In others you get healed by an NPC and you're expected to just deal damage to clear the battles.

The classes quests are more story than training. In terms of training value, class quests are a complete failure in implementation.