How does precision help condition damage Mesmer
To answer your main question in general, here is a quotation from the wiki:“Precision is an offensive character attribute. Attribute points put into precision increase the chance of a critical hit for the character. Many of the conditional effects of a skill or trait trigger on a critical hit.”
So extra precision helps to trigger conditions more often through critical hits. Now, you can ignore my answer easily because I don’t actually play mesmer- class and I don’t know how many skills this class has which trigger conditions on criticals :P . However, if you have such skills the upgrades including precision will indeed help you.
For necro (who’s precision on crit abilities are easily the worst in the game- a 1 second bleed) the appeal is sigil of earth.