I am level 26.

What you're wearing stat-wise still matters, since it scales with the Bolster buff.

You want to wear the best you can get your hands on and obviously the stats should be class appropriate. The closer the items match to your level and the quantity affect bolster. For example I recently twinked my shadow who was around level 26 with 90% purple mods and armorings and despite being light armor non-tank that toon had top or #2 health in every wz for several levels.

Of course it matters. Even with Bolster, your gear still adds stats.

 

Specifically: If you're a tank, then you want gear that is going to set up your shield/defense bonuses so they get properly bolstered. Healers will want their alacrity gear, Marauders/Sentinels will want to choose their Power or Crit gear.

 

From what I understand, the game tries to scale your current gear to a L49 version. I wouldn't be surprised if that means that your L26 trash green gear gets scaled to L49 trash green gear. It's better... but you're still going to be out-geared by everyone else.

Also if you are mainly doing wz only it's worth investing in a level 10 +41 expertise crystal. It's the only way to get any expertise until around level 30 I think.