WvW sigils
The Sigils really based on your playstyle. Personally if you are going Grenades sigil of earth is the best. However, if you are going close range with P/P & Toolkit then Sigil of Geomancy (not Generosity) will do more damage.
Also with upcoming changes the might stacking sigils will be less effective due to boon hate/steal.
I’ve done some analysis of the Earth & Geomancy sigils here:
https://forum-en.gw2archive.eu/forum/professions/engineer/Superior-Sigil-of-Earth-or-Geomancy/first#post1785813
Davidah (Guardian) Goloith (Engineer)
Achuni (Mesmer) Doreanora (Thief)
To add to what Goloith said, Earth would be the best in a ranged/condition/grenade build, and it will sync nicely with the Shrapnel trait, or the Incendiary Powder trait, and the Shrapnel Grenade.
Sigil of Geomancy is more for a tanky condition damage build, like Rabid gear or Undead Knights build.
I personally like the Sigil of Hydromancy for an offensive swap because it scales a tiny bit with power and can crit, so in addition to slowing them for 3 seconds (seriously OP), it can also proc conditions.
Physti – Elementalist | Fistful of Blades – Thief
[WHIP] Quaggan Slavers – HoD