No 330 and only Rt/Mo? Off the top of my head (no idea if it will work or not, never tried to farm them) you could try maxing out Communing and Channeling and take [skill]painful bond[/skill], [skill]pain[/skill], [skill]bloodsong[/skill] and [skill]anguish[/skill]. Drop pain and bloodsong in range of 2-3 of them, and drop anguish in range of another 2-3 and use painful bond to up the damage from it. Let them do the work. Could add in [skill]nightmare weapon[/skill] as a wanding attack if you're waiting for recharges. Energy should be fine since you're only using 3 spirits and 2 spells, only one of which is expensive (anguish).
Like i said, off the top of my head with your restrictions it's the best i can think of. No idea if it would work or not. It'll definitely kill them fairly easily but i've got no idea how the drops would work using offensive spirits. Just make sure you wand each worm at least once to make sure the game knows you were doing something to damage them.
Might try this myself actually....see if it works. Got me curious now.
EDIT:
Just tried it in HM and it works quite well. A couple of slight ammendments though. Put all 3 spirits one on top of the other in range of 3-4 worms (don't forget that spirits have longbow range attacks), cast painful bond on one and recast on the other as available. Use nightmare weapon to add extra damage.
Now, here's the interesting bit. If you wand each worm before they submerge, the spirits will continue to attack them and even switch to the next target even when they are submerged. You don't have to wait for them to re-surface, so long as you have wanded them at least once. Cool eh? lol
Took me about 5 1/2 mins to kill all 13 (until you run into the pinesouls) from leaving boreal station with no speed boost. Seems to take 4 drops of spirits to kill them all and your spirits will have recharged easily before you need to move on.
That's 5148xp every 5 1/2 mins without scrolls and totally risk free. Even if you err007 you ain't gonna die because the worms are never close enough to hit you. Drops aren't all that great though but if you wanna farm them with a rit i'd say this was a
very easy way to do it.