Its pretty decent, cause it STACKS (which means 3rd and 4th attacks just wreck stuff)
And as long as you are healing up nicely, it allows you to get close to 100 with 2 or 3 potions)
If block created a permanent reduction (for that battle) it would be on par with heal, but as it is, its almost worthless.
Poison, is only useful in long drawn out battles, and these arent even remotely long enough...
Damage to all, is way too low to be useful, sadly. If you were planning on making parties bigger, on both ends, perhaps...