@munakata being better would be understandable. What he does is completely over the top unrealistic.
I've played a fair bit of MMO and i was a raider in WoW for years. Unless you are really overleveled a raid boss or zone boss with recommended party are DEATH SENTENCES for any solo player, no matter how skilled, because their stats and abilities are TUNED to NEED a party to take them down.
To give you an example: in the starting zone of humans in WoW the final quest was originally a fight against an elite mob called Hogger. The quest told you that it was recommended to fight him in a party.
Hogger became infamous for the sheer amount of deaths he caused. It reached such a ridiculous memetic status that Blizzard added a special counter in the "Deaths" tab of the info menu of each player, called "DEATHS BY HOGGER".
He had very few abilities and he was a few levels higher than the rest of the zone (befitting his status as a minor zone boss). He simply PACKED A PUNCH due to his higher stats.
A world boss like Lucaorn? Unless you are a tank (and MC here is the opposite of a tank) you are dead in a few seconds, because even the most basic attack would deal enormous amounts of damage.
It's like putting a Navy SEAL specialist armed with a rifle against a TANK.
No matter how skilled the soldier is, he has no hope of surviving that amount of firepower.
(edited for more accurate example)