There are factors.
#1 ... minimum base 30 intelligence when using any heal charms that are less than 150% EE.
#2 ... Salvation is great, but of off class, you will spend 5 minimum ability points = 40% charge.
Now Bigheaded is correct with the monsters that remove abilities, there are those that ONLY remove healing abilities and only melee abilities (that I have come to notice so far)... there are also those that will remove both types instantly, and those that remove both types one at a time.
Note: I still have to keep testing this... the monster types with eyeballs seem to be a biatche ... not sure if it reacts to removing abilities based on it being hit, or a % chance based on RNG.
Personally... test it out for yourself... also... if you get to Warlock, having the Heal type charms is going to come in handy.
I solo only on HC, I always use Salvation and a minimum 30 base Intelligence even for a Samurai. upwards.