This is an interesting question. Temperance seems to give a lot of value in terms of versatility, and avoids lockout from Siren Soothsayer if you have a balanced-ish party, but I can’t see that scaling too well when you’re outleveled. Wreck is really nice for an individual creature, since Health gets more points per enchantment slot than Attack and also helps you out defensively. Of course, Swiftcasting is crazy useful since it allows you to make Speed even better and makes a lot of parties more viable. War Forged will also help out a lot of parties with no questions asked. Oh, and speaking of Siren Soothsayer, Filtered Truth seems real powerful. If you’re not specifically set up to counter it, it’ll neuter you, even for Burn/Poison reliant teams and the like.
Affluence is also real good. Assuming you’ve bought the three extra spell gem slots in the perks (I have no idea why you wouldn’t) and modded your weapon for two extra slots, it’s 400% extra damage – and the ability as written makes no distinction between permanent and temporary spell gems, so you can trick that out even further. Cold Touch cripples a lot of things. Everglow is good by itself and helps put a lot of spells, buffs and traits.
If you’re the type who runs Tribe parties (or single-type summon party), Pharaoh’s Boon is pretty alright for 60% extra stats across a party for a legendary artifact slot. Similarly, Solace, Darkness Fate, Dark Aegis, Primitive Incantation and Thaumaturgy are great value.