Always intresting to read these thoughts on HP and AC and for grouping I agree with the above posts. Basically you wear the best gear you can get - it is simple. When it comes to raids and pallies I would suggest max hit points and max mana. I suggest hp for the ae dots you will experience - from like babs in fire and mana for all the sup healing you will do.
I know i spam the MT as fast as i can on every named mob until im oom or I feel the clerics have the rotation under control -so mainly till oom.
On high end raids you as a pally should not have to tank (unless a special pally pull mob we have one in Tactics)your guild probally has 4-5 warriors rdy to go defensive, plus if you are spamming the MT with heals and perhaps a lay hands and that MT dies - kiss your **** good bye when you get hit 5 times for 1500 or more.
my suggestions to the raiding pally:
wear the best equipment you can get
max out lighting reflexes (aa points)
max out crit heals (aa points)
don't get aggro unless your told to
keep everyone buffed with BSS