Holy Shock, as an instant cast...
With the GCD reduced by your haste rating.

And without any form of a cooldown.
Assuming you take that talent.

With 5x Shock'adins...

If Pallies have enough damage to kill single targets in succession, assuming a 4/5x group...
It might not be a bad idea to run 5x heals.
You'll have very good survivability, but lack a bit against cleave compositions.

Still, my 1x Pally... on the Pally/4x DK team, can be pretty scary in the amount of healing output she does.
Imagine having five of those.
And the ability to do some decent damage, even if you're taking out opponents one at a time.
My 5x Resto Druids can consistently take out 2-3x their number, anytime players ignore CC, and go for straight damage based killing...