Summon Soulless - Phantom Summoner questions

I have recently completed the job transfer to PS and am now level 44. I have picked up the spellbook for summoning the Soulless but I don't understand its usage. Let me elaborate:

The Shadow can hit harder and take more damage, costs D crystals to summon and sustain. He also has a sort of Vampire Regen effect that is on constantly and does not require the expenditure of MP. He takes 30% exp.

The Soulless on the other-hand is killed quickly, doesn't do too much damage and costs C crystals. He has a poison cloud aoe spell (So do I) and a Corpse Burst. He takes 10% exp. He also DRAINS my MP constantly!!!

I have heard some folks call the Soulless a "Hearding" summons. WTH is that? I know there HAS to be a reason he costs so much to summon and maintain but I haven't got a clue.

Can anyone point me in the right direction? :(

The souless hits harder then the shadow, but for "normal" exping use shadw due to the passive vr. Unless you have a buffer with vr.

soulless costs so much to maintain because he only takes 10% of your XP. He does about 10% more damage per hit and uses fewer soulshots. Soulless is designed for use in groups and his spells specifically are AOE oriented. You can solo with him but only agains fairly weak mobs that drop herbs frequently.