I used
iZakaroN's SaveEditor (or from
Kiya's site, with description) to give new characters of each class hundreds of free stat points, and for the offense and defense table, enough experience to reach level 50 (see
here). I added stat points to individual stats and observed the listed results, using a spreadsheet to determine the formula that the game used.
In the descriptions for the offense and defense (at least for the disk version of the game), the chance to hit and be hit is based on an average opponent your own level, so the agility and level of individual opponents will effect the actual chance to hit and be hit.
Since opponent stats are effected by the difficulty level, that also influences the listed chance to hit and be hit, though the formula for the secondary stats, offense and defense are the same regardless of difficulty setting. For example, a survivor on hard at level 50 would need an agility of 175 to get the chance to be hit down to 19% and 186 to get the chance to hit up to 94%.
Playing a warrior on normal, I ended up averaging 2 stat points in constitution per level (I also favoured vitality bonuses on equipment, after the armour rating or damage where applicable). Hell Spikes could do some damage mid-game, but traps were not much of a problem after the beginning of the game. Spell Shield can help with traps and poison, while Aura of Guarding helps with Hell Spikes and other physical damage (I maxed both with purchased spell books; and used them for awhile mid-game).
