also the ability to survive high falls allows you to use a few shortcuts.
actually fall damage in dark souls is percentage damage, it just takes a % chunk based on what your equip weight is (the more you're wearing the larger percentage of your MAX health it takes). you can survive the same falls with 10 vit as you can survive at 99 vit, there's a cutoff point however where any falls from above that height are 100% damage fatal. Naked with 10 vit falls actually do next to no damage to you
Rolling when you land the fall also reduces the percentage of health it takes from you.
For stats, there's really no reason to go beyond 50 in any stat (or go beyond 0 in the case of the "resistance" stat...NEVER level res), no reason to go beyond 40 actually unless it's a weapon requirement, or on one of VERY few weapons that dont falloff too badly until then (biggest example is the crystal catalyst, which the ideal stopping point is 50 int), theres really not much reason to go beyond level 125 either, beyond that the online interaction plummets as ~120 is the "meta" for dark souls, it's the general stopping level for most people and where you'll get the most pvp and phantom summons.
For the 4Kings fight, it can be pretty hard with slow swinging heavier weapons as you'll often get hit mid swing, so you really have to stack poise as much as you can but try to keep at least midroll. Especially NG+ and beyond 4k and gravelord Nito in particular you can no longer really "cheat" them by poise tanking (you "kinda" can in ng+, but not really beyond). 4K does more damage the further from them you are so you want to stay close and juse dodge the swipes as much as possible, when they glow roll back and keep rolling back until their dash stops, then get close again quickly or they'll run ans start shooting homing purple crap that does a ton of damage. Like most of the bosses 4k is actually a LOT easier with smaller, faster weapons, as it's easier to keep hitting until the last second then dodge, plus faster weapons get more out of weapon buffs as the buff damage is static, it doesnt scale by the weapon, and for 4k you should be using gold resin, sunlight blade, or any other fire or lightning based buff as that's their weakness. Speed and buffs are the biggest key to taking any boss down quickly and easily in dark souls, a buffed katana or similarly fast weapon easily makes it a "three kings" fight even in later ng+ loops as you kill them so fast you have time to rest between kings and the 4th never has time to spawn!
If anyone is on ps3 and would like to co-op a boss and have me show you my tactics first hand I would be more than happy to as well.