The only part of it that seems outdated is the Zombies section. Every other section is fine.
In PvE, you get XP per damage dealt to a boss.
Let’s say you deal 20k DPS to King Slime, which has a DP multiplier of 0.002.
\text {20,000 Damage per Second} \times 0.01 \times 0.002 = \text {0.4 XP per Second}
Keep in mind that the sign command in PvE summons multiple King Slimes.