I carry two extra sets of armor, one with Runes of Earth and one with Runes of Mellandru. My standard set is Runes of the Forge. I put on Earth for Ranger/Eng teams, and Mellandru for Mesmer/Necro teams. I also swap to a crit amulet and Sigil of Purity vs. Mesmers and Necros, and a Sigil of Nullification against 2 or more Guardians. I also change up utilities, swapping out Throw Mine for Tool Kit (again vs ranged heavy teams) or Elixir Gun (Necro heavy teams).
My question is, how much pre-match tweaking is too much? I feel that I get countered hard by necros and mesmers, which is what started all of this swapping.
Do any of you do this in tPvP? If so, how much and what exactly do you bring to shore up your defenses against builds that straight up counter you.