The battle with the 4 warders is one of the toughest I've faced in TotSc - you're not alone in trying to nail those 4 creeps

!
Before the battle, I cast all the protective spells in my mage's and cleric's repertoire, especially Haste, Bless and Protection from Evil 10". I also placed my skeletons from Summon Undead to the west of Love so that they can intercept the dangerous fella under the Holy Might spell. Then I position my invisible thief behind Love (the only visible guy before the dialogue), start casting Entangle at the NW area (to ensnare the backstabbing dwarf, hopefully), and initiate the dialogue. Once the battle has commenced, I concentrate all my attacks on Love - I find Haste to be particularly useful here, since it maximises the no. of attacks my party dishes out. Next to go is the NE dwarf, as he is probably already whacking at your nearest character. I took out the NW guy with missiles, since he was simply too dangerous to let near my characters. Same goes for the backstabbing sneak (I also use Detect Invisibility at this point).
Throughout the battle, my thief (enhanced with either the Strength spell or with potions) was zipping in and out of the front-line so that he could backstab as many times as possible.
All in all, I reloaded about 4 times before I killed all the creeps without any casualties.