Heal doesn't really help all that much for a Sorceror.
Personally I'm not even sure if it returns the caster any mana. Pretty sure I have my Heal maxed (too lazy to check) even now and whenever I cast it it seems to take 5% mana that regenerates back to the original position in like 5-10 seconds. That's with naked 500HP worth of STR and the rest in INT.
On the actual Heal usage I feel it's worth it to take the strain off the tanks who in turn keep you alive by keeping the aggro. It might not feel worth it in the beginning but the higher level bosses and the new updates sure bring in the whole different game.
EDIT: Checked the skill and I had all but the range extender update. The regular heal costs 5%, but a charged one (as said in description, i had just missed it) returns 5% extra, meaning 10% total if you take cost into account.
The mana regen afterwards is not really noticeable, at least not with my mana pool. Maybe it's more useful in the lower levels where some +5 regen actually helps.
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