Vanguards/Powertechs, Guardians/Juggernauts and Assassins/Shadows. They can all tank. But at roughly what level does gearing and talent choices really start to matter when tanking heroics and flashpoints?
If say, a Vangaurd is geared and talented towards dealing damage instead of survival (choosing more Aim instead of more endurance, going down the Tactics or Assault Specialist talent trees), at roughly what level would healers have trouble keeping them alive for heroics and flashpoints?
Up until around level 20 you can tank any flashpoint in DPS gear and DPS talent spec if you’re in the tanking stance.
At level 30, you can stay in DPS gear, but you’re going to have to go at least hybrid into a tanking tree, and keep the tank stance on.
After level 40, if you’re a good tank player, you can still keep the DPS gear on as long as you start using your shield generator and have around 10+ points in either the Tank tree, or 15+ in the Combo tree.
At level 48 you’re going to see a big change in flashpoints and your armor is going to have to change also. You’re going to have to start working in more mitigation gear and lose the DPS gear.
All this is predicated on you knowing how to tank; not being a DPS player ‘trying’ to tank. If you’re new to tanking, then be a tank. Let your DPS kill stuff while you keep them safe. If you’re an old tank and just leveling a new version, then you know the ins and outs of the role and won’t see a huge problem if you want to boost your DPS to speed up your leveling.