I'm a lvl 19 necro and I've saved up for one jasper; I want to adept III a pet. Which pet should I upgrade, grim spellbinder or the tank at lvl 24? I know the conventional wisdom, it depends, if you group then blah, blah, blah... but which pet would you upgrade given the choice of just one? Opinions?
If you had one choice and one choice alone, Undying Adherent, no question. Be sure to check out my Necromancer Adept III list to help you decide on future upgrades. Personally I would go all out harvesting, trying to get more Jaspers and Palladiums for your Adept IIIs.