There are a few rules if you want to gold farm in Guild Wars. These are completely different from the rules in Guild Wars 2.
First you need to remember that the drops are divided among the members of the party, even heroes and mercenaries. So, the fewer members of the party there are, the better. There are “leechers” which are members of the party that stay far away from the action, and allegedly improve the drops. But they aren’t helping you kill mobs. So if you are solo farming, they aren’t useful. Do you have friends who don’t want to play, just stand around?
Second, you can employ pets and spirit helpers with no loot penalty. So a Ranger / Ritualist or a Ritualist/ Ranger seems like a good build to use for solo farming. Here’s the build that I use.
Update: What you really want to do however, if you are level 20 with strong heroes, is vanquish the area in hard mode. See below. But back to our story in Normal Mode.