Prayer, Cleansing and Meditation are
not synergized. The only synergies are the 3 Druid summons (and they
do include softpoints).
Telekinesis also is
not a synergy: Energy Shield takes 2 mana for every point of life it absorbs.
Baal's beam is a
single missile that deals 512-544
magic damage on Hell. But since your Magic Resist is -100 there (caused by the difficulty penalty), it will deal
1024-1088 magic damage. Like anything else, this missile
can crit for 2048-2176.
MDR will reduce its damage, but since it is only one missile, MDR gets applied only
once to this massive damage.
After MDR has been applied, ES will reduce the remainder of the damage (but not before the beam takes 50% of your current mana!).
The stuff about Laying of Hands and 4-frame hit recovery were all myths unfortunately, none of that will help you.
The conclusion.. Avoid that beam.

Otherwise, your only options for protection, like pharphis and zemaj suggested, are high life, MDR, and ES.
And a quick note on ES: Whenever incoming damage "activates" it, it uses your
current skill level, not the skill level from when you cast it. So if you cast ES with a +3 ES staff, and then switch away from that staff (or remove it), ES will lose those 3 levels. If ES is level 0, it will still display, but not actually do anything.