What level are you, and what character build?
Did you try lowering the difficulty, if you are not already playing on casual?
Have you summoned your creature (and a summon, if you have one)?
If you have any equipment with a bonus to a summon skill (I found a couple with Summon Demon bonuses) you can equip it long enough to summon, then switch back to your regular jewellery.
Using Charm on one of the opponents could help, as well.
Temporary potion or spell buffs could also help.
With Stone, are you having trouble in the first section of the headquarters, or in the arena? In the headquarters, in D2:ED as a warrior I focused Stone at first, but ended up dying. After reloading I concentrated on the other opponents there, leaving Stone for last, and did much better (though someone else posted with the opposite experience). In DKS as a ranger I didn't have much trouble, but I left all of the headquarters until I was finished the rest of the flying fortresses (wanted to delay doing the dragon parts of the fortresses and completing quests).
In the ministry I stood a little in front of Zandalor, with my creature at least slowing down the crawlers from the left portal. Whenever there was a break from the front 2 portals I would check behind me to see if I needed to take out a memory eater from the back portal.
As a warrior in D2:ED I used a bow to attack opponents from the front rifts (primarily the right, as my creature handled the left rift there, as well), more to get their attention and draw them to me than to do damage.
