These were my top 5 in the top sticky, though I didn't explain why.
1.
Sol Ro, with Ro's Fury and Incineration
2.
Bertoxxulous, with Pus Bolt and Pox of Bertoxxulous
3.
Cazic Thule, with Thule's Blessing and Id's Release
4.
Karana, with Blessing of Serenity and Unyielding Ice Storm
5.
Brell, with Earth's Vigil and Rift from Below or Forgehammer
Basically the reasoning is, you want nukes and damage. Inny is not bad if you lack power, but mostly you shouldn't. As far as other things than nukes and damage, there's not much else you can gain really, although Thule's Blessing (which increases chances of landing a spell) can be useful in limited raid situations, and Id's Release (ae fear, unbreakable) is really useful soloing. The rest are just kind of fun or extra, but don't help necessary in everyday situations.