Keeping a high level cleric alive:
1. Expect Spell Resistance. Assay Resistance (CD, CA), Spell Penetration, Greater Spell Penetration, and the orange prism ioun stone are your friends.
2. Buy fortification armor. You can always cast magic vestment on your armor to boost the AC bonus.
3. Buy a resistance item as good as you can afford.
4. Get a luckblade with no wishes. Rerolls are essential because, sooner or later, you will roll a 1. (No wishes isn't essential, it's just much cheaper without them).
5. Unless you're built to be a fighter, don't try to be one. You're much more effective casting Heal on the real fighter after he takes 120 points of damage in round 1 than casting righteous might and divine favor and divine power and then saying "if you're hurt, stand behind me and let me do the beating."
6. Use your spells to buff yourself and your allies. Hero's Feast. Magic Vestment. Greater Magic Weapon. Magic Circle vs. evil (keep the summoned creatures away). Freedom of Movement, etc all have fairly long durations and don't take up slots that are first tier offense by 17th level.
7. Knowledge skills are your friend. Use them to get info about the monsters you're fighting. (The three most useful ones at high levels--Arcana, Planes, and Religion are all on the cleric spell list).
8. There are no p-classes in the Complete X books that make you survive better without sacrificing spellcasting ability. Sacred Exorcist and Radiant Servant are both very good, but neither give you more hit points, AC, or combat ability. The way prestige classes will contribute to your character is to give you more options not to make you a fighter.
9. Find a way to get a constitution boost. You will need it if you want to keep your hit points up.
And, to answer one claim:
Jdvn1 said:
Well, at high enough levels, you can't boost your AC high enough to help against high BABs. So some people recommend just not giving effort in the AC department.
There's a big difference between getting hit every time in a full attack action, getting hit every time while power attacking for 5, and getting hit once or twice.
Going from memory, the Ftr 20 that I statted up for the Fighter/PsiWar thread had a full attack of +38/+38/+33/+28/+23 or so for 1d10+23 points per hit. Now, it's easy to look at that and say "I still get hit on a 2, what's the point of my AC 40?"
Well, AC 40 gets hit for an average of 111 points of damage on a full attack without power attacking. But, let's say your AC is 35 instead of 40. Without power attack, you take an average of 137 points of damage. If he power attacks for 5, that goes up to an average of 144 points of damage. If your AC is 30 instead, that's 178 points of damage per full attack with a 5 point power attack (and the number is pretty constant between a 5 and 10 point power attack so it doesn't take much finesse to get good results).
So, losing ten points of AC increases the damage you take by about 55% or so.
The difference is even more dramatic on a sinlge attack. If the fighter has to move to get to you, it's the difference between taking 33 points of damage (optimal power attack for 1 point) and taking 55 points of damage and making a save vs. massive damage (not hard, but you can still roll a 1).
Incidentally, AC 45 (+5 mithral fullplate, 16 dex, rose prism ioun stone, +5 ring, +5 natural, +5 heavy shield, haste or dodge feat) knocks that fighter's full attack to about 72 points per round. At 17th level, that's the difference between "I'm dead next round" and "I can take another round of this before I have to worry too much." And that's a huge difference.