Lasermaster: I don't know if you still have a problem with this but here goes.

One big thing you have to ddo to beat the old ghosties is to learn how to avoid thier attacks. Now it isn't really reasonable to avoid all damage but you can't face-tank as the Warlock. Also you can attack the statues in the Arena to deal damage to the ghosts while they are immaterial.

I'd advise you to try the other classes. That way you can unlock some more passive bonuses via Class Titles. When you beat a boss for the first time with a new class that class grants every heroe a small permanent buff like The Paladin gives everyone a bit of armor.

Also the Warlock, at leaste in my experience, needs a lot of levels to real get going. So that's a bit of a challenge.

Have you tried messing around with the Fountain? A lot of the effects from it can be very helpful.
I'd recommen the larger floors buff as it give you more baddies to kill and loot to find. THen adding on the more chest and glass walker buffs once you can handle enough debuffs to pay for em.

In my oppinion the add more enemies "debuff" just make the game more fun so I'd try and see if you can handle having tuning them on. Also onother ez combo is the "potions make you confused" debuff and the "you are immune to confusiion"-drink, confusions is IMHO the deadliest status effect in the game so getting some free Fountain points while stacking immunity to it is just good sense.

PyreBall: Sorry this reply is so late, but I managed to get it not on my warlock, but my priest, who is a few levels lower. And I did mess with the fountain, but like I said, I used it to up the number of potion charges I had since the chance to spawn a refill fountain seems absurdly low in those stages.

Lasermaster: Oh I don't mind at all I just hope you got some use out of my post.

Pots are pretty important for the spellcaster classes as they give you back mana as well.

It takes a fair bit of work but if you want to break away from that dependancy on potions I'd try a class like the Rogue or Ranger and get the Lifesteal Blessing. That way you can get life back without pots and you'd be able to try different Fountain combinations.

PyreBall: Ha, that's actually exactly why I went for the priest. Unfortunately the healing abilities don't work all that well as self heals, particularly when your health is naturally low because of the class :P