Alright. So we take out dampening and make it so you can only use GoG and AoD on one person at a time each. The Enchanter spends their ~5 second casting those two spells, and now they are waiting 19 seconds for the first one to come off cooldown.
What do they do with the rest of their time and all that mana they have? Can't do that True Giant thing because GoG has already been used (ignoring reuse time is not possible because of the client). Spam rune? What fun things are there to do in the meantime that will make people want to play Enchanters where there's nothing to mezz? WHAT utility in the downtime?
Either code it so that aod+gog can only be on two targets (ignoring enchanter), but the cd remains 0, or just make true giant trigger off a different spell (hell add back in self only Gift of Giantkin, True Giant was a cooler name anyway)
Enchanters can then use runes, vex, catatonia. I'd be all for adding in some new spells here to make the enchanter feel more active, useful, and interesting without adding crazy amounts of dps. Potential spells that could get added:
A healer version of aod/gog - 20% spellhaste and 20% extra healing. - would also only be on 1 person at a time.
A targeted -agro spell, so wizards or rangers dont have to spend as much time jolting.
Any short duration debuff (- accuracy, -AC, -resists, etc)
A Target's Target gains +1000 agro to make Pally/Warrior tanks more viable on max burn raid targets.
There are lots of fun little things that could make an enchanter feel really useful (and without a doubt they would be), without making them such a massive dps contribution that they are required.