By Attabrain Zee, from server 4. Updated for 2.7
Enchanting in DragonSoul requires a lot of money, and you have to destroy some equipment to do it. So when do you enchant?
Enchanting only makes your heroes a little stronger, but that little bit can make a big difference. Unenchanted heroes will lose fights in the pit and colosseum, and it will be very hard to move up in the ranks. Higher fight pit and colosseum tiers means more diamonds and tokens, and both of those are worth much more than the gold and equipment you lost by enchanting.
When you promote an enchanted hero, you only get a fraction of the enchanting stones back, and none of the money. So you waste both money and resources.
Do it when your hero is at the highest promotion level he or she is going to get to for a while. Let's say you really like P+2 on a hero because of the available equipment – for example, Megataur's conservation boost at that promotion level makes him very powerful. That's a good time to fully enchant. Or maybe you've reached the level cap and have a hero at max promotion, and the next cap raise won't be for a month or two. Nice time to enchant. Or maybe you're just doing horribly in FP and colosseum, and you really want to move up. Then get yourself a good enchanted team.
Look at the stats of the piece of equipment you're considering. If the equipment gives +10 intellect and +10 armor, and it's for your tank, why waste all that money? But if the item gives lifesteal, conservation, or a lot of health (or strength – you get 18 times your strength score as health), then it's probably worth it. Now whether you want to enchant to 5* depends on how generous you're feeling. A 5* enchantment now might mean you can't afford another 5* enchantment next time you promote. That's part of the game's strategy.