There are a couple places in the game where enemies respawn before entering the Hall of Echoes, and more after that (though I have not played FoV yet, the end section of DKS).
In the D2:ED part of the game, spawned opponents are relatively weak, so you need to either wait or trigger them repeatedly to gain experience at a reasonable rate. The first spawn points are:
Broken Valley, Maxos Temple, mirror room test -
clicking on a certain barrel spawns opponents. I never noticed this in D2:ED, since I destroyed all the barrels and crates with a bow.
Aleroth, ministry -
allow opponents to get to Zandalor and more will keep coming through the rifts
Orobas Fjords, Keara's Flying Fortress -
trying to open the inner door in the headquarters without solving the statue name puzzle will spawn opponents throughout the outer headquarters. This is the best place to spawn opponents (you can click on the door multiple times and then go fight), though not available until later in the game.
In FoV I think there are caves that respawn opponents every time you enter.
A previous forum discussion on respawning took place in the topic
WTF GARBAGE, and a couple other places.
Welcome to the forum.
