Echo Caverns (level 22 - 31)
There are two sides to Echo Caverns, totally separate, with two different entrances. The first is reached by walking through a wall in the rogues guild building in Shadowhaven, with an entrance next to the Soulbinder, and is suitable for levels 22 - 35. The second has an unhidden entrance through the Stout area (south of the Nexus portal), and is good for level 35 to 50. I'll be dealing with just the lower of the two halves for now.
Once you zone in to Echo, turn left and follow the passage, passing through a guarded door (ignore the curtains leading to the mutant area). The rooted tentacles are traps, and will severely harm and even kill a low character, so pass them with great care. They cannot be targeted or fought. You pass through the boglings, which are too high to fight at first. Boglings will aggro if you get too close, but their aggro range is very short. Past the first set of boglings take the passage to the right - a higher level bogling area is straight ahead, which you want to avoid. Take the next right; if no one is hunting there, you will find a room full of needlites. At 22, they will be even through to red - but can be fought singly, all apart from one pair.
Stop on the ledge next to the tentacle trap before dropping down into the room; there is a needlite spawn immediately in front of you in a dip that will be hard to see if you don't already know it is there. To your left along the room wall is a spot where it is always safe to sit and meditate. Summon up your pet and buff up, then med to full. When you are ready, drop down and kill the first needlite in it's spawn location.
No real strategy is involved here, just always remember to drowsy them, as they hit fast - but very softly. Once the pit needlite is dead, move to your left to the safe spot. Then kill the needlite immediately in front of you, then the one (or is it two?) behind him. The next two going anti-clockwise are the linked pair. Kill the one by the entrance next, and leave the pair. When you are happy killing the single pulls, try to split the pair; once it is split, you will be able to handle the spawn very easily. To split, cast flash of light on one, and kill the other; recast FoL when it wears off. It is best to FoL the normal needlite when it is a queen pair.
The near two of the pair will often spawn the Needlite Queen. She is slightly higher than the normal needlites, about level 27, and will cast a weak dot on you. She drops a wing that sells to merchants for about 7pp and is a low level caster back item, and a needlite dagger, which may be a decent piercing weapon to keep. Needlites in general are level 22 to 26, and may drop legs and wings (both stackable), which sell for around 2pp each. This isn't a rich camp, but very much better than Paludal would have been anywhere apart from the bandits.
Respawn time is around 16 - 18 minutes. At 22, these will be tough fights, but you should just about be able to kill the 5 singles and recover in that time, for almost a yellow per spawn. At 30/31, some of the needlites will become light blue, but you will be killing the entire spawn (easy from about level 27) and experience will start to seem slow - but it will still be as good as anywhere else you may find at this level.
Remember at 25 to go to the trainers in Shadowhaven (the secret portal by the Nexus portal) and train one point in block.
If there isn't any competition for camps (which isn't very likely), you will be able to move back and forth from the needlites to the first bogling area, and kill all 4 boglings as well as all needlites per spawn cycle. I haven't hunted the main bogling room or the saprophyte room, both of which are tougher with multiple pulls, and need a dedicated group. I also haven't hunted the mutants.
Echo Caverns (level 39 - 49/52)
The far side of Echo Caverns contains underbulks, fiends, undead slaves and gnomes. The first set of underbulks (to the left and down the lift when you enter) are killable in your mid 30s, but all the rest need high 30s and 40s to kill. The guards in the evil trainer area are also apparently good hunting. The main set of underbulks and fiends will turn light blue during your high 40s, but the Taskmaster room stays dark blue until 52. I suggest starting here at 44, with Spiritual Light for regen; there are better places at lower levels, notably the cave basilisks in Jaggedpine. Starting earlier at the four underbulks ledge with KEI is certainly an option. The four underbulks at the elevator are much lower level, and could be used to fill in the level from needlites and boglings to the underbulk ledge.
The first room heading straight back past the gnome area contains a four spawn of underbulks. This is the area to start in at any time in your low 40s; and is certainly possible in your 30s, but not as attractive as Dawnshroud because of the slow spawn times. To pull these, start from the near end and pull one at a time; if you get two, in an emergency use flash of light to send one away; with luck, it won't aggro any remaining. The main problem here is trains of Fireclaw/Trillcor, usually from the Deep room; stay alert. In the other rooms, some of the spawns are hard to split. However, if you pull using either Cancel Magic or simple proximity aggro as I suggested for the shrooms in Dawnshroud, most of the time they should pull as singles.
The Taskmaster ante room has seven spawns. Fireclaw or Trillcor can spawn on any of these, give no extra experience, but are much harder to kill. Trillcor has no loot, unfortunately; Fireclaw just his carapace and talons. Some stonegrabbers will turn green at 46, then at 48 about 50% of the mobs will be green. However, because your pet is now grey, it is well worthwhile staying here through 48. Levels 44 to 47 should take 4.5 - 5.5 hours each; 48 5 to 7, depending on the luck of how many greens you get per cycle. The only spawns that you need to take care over splitting are the two as you enter the chamber - pull the one at the bottom (near side) of the room with proximity aggro, and he won't path back up to the next spawn point. Spawn time, in both sides of the caverns, is approximately 18.5 minutes. You should be able to clear the entire room within the repop time from 44 onwards.
The room next to the Deep zone line has eight, possibly nine spawns. Three are fungal fiends, four are underbulks, and the remaining one/two can spawn anything, including the named. One of these last two tends to wander about the room, and can wander into a fight, or into the middle of the three spawn of fiends, making them hard to pull. I have always been able to single pull these, but I have hears reports of people getting multiple pulls even at 48. Just always take care to pull directly away from their friends, and use proximity aggro if you are uncertain. If the nearest mob is a dark blue, they are more likely to aggro than if they are light blue.
At the lower levels, 44 - 46, I could only melee for a few seconds at a time; I'd melee down to 70 - 80%, then back off. Healing myself beyond this consumed more mana than I could regenerate in the down time. At the end of a spawn cycle, I'd usually let myself get low in melee so that I could practice bind wounds. At the higher levels, I didn't need to worry; most of the mobs, apart from the highest dark blues, would only take me down about 20%, even if I melee'ed through. I would always pull with Drowsy, cast an Envenomed Bolt and Ice Spear on all but the stone grabbers. For the stone grabbers, they resist all casts apart from Drowsy, so either melee them or stick to playing pet cleric.
The Taskmaster room will be all blue at 49, with a few green slaves at 51; beyond that, only the Taskmaster himself will remain blue. If you want to pull the Taskmaster from a full spawn of slaves, only the one on the near right will come with him, so it is best to kill that slave first; at higher levels he may pull singly. The slaves to the left will also usually come as multiples; having a cleric, bard, paladin or enchanter partner to pacify them will eliminate this problem. At 49, you can pull these as singles with Cancel Magic; the middle two on the left sometimes come together even so, but two at 49 aren't a problem to handle. The Taskmaster drops (always) a cracked shissar revenant skull; no one knows what it's for. He also rarely drops shissar organs, which are used in the quest from Katta for the Amulet of the Gray Wastes; you need three for this quest, and good races only need apply. Polished scales are vendor loot; the orb of echo ore is a nice range slot Bazaar item.
The gnomes are also blue at these levels; I haven't fought them, but I believe they give good experience if you can discover how to split them.