Guild Wars 2

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 gear 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.

A little more explanation:

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 heavy teams, and Mellandru for Mesmer/Necro heavy 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).

P.S. Our team played two back-to-back matches against the same team last night. They had 2 Necromancers, 2 Mesmers, and 1 HGH Engineer. I have to say, I was glad to have my Mellandru set and the Rabid amulet for higher crit to trigger Sigil of Purity.

I just want to bump this one more time. It got no traction on the Engineer forum, but I assumed it was because it was tPvP focused. Does anyone have any opinions or feedback on this question?