Andor's Trail

When grinding for exp and legendaries, one of the most annoying things is the wait time for fresh spawns.

How about the introduction of a potion that can considerably increase the likeliness of respawns (I know, probably takes an engine change).

I like this idea. It sounds reasonable.
Maybe have the potions available after completing a new quest.

A similar potion could cause all mobs to aggresively seek out the player, so they form a mob, and facilitate clearing large amounts.

or you could simply make the same potion has both a "positive" and a "negative" effect.