I haven't played CoH/V since Villains was released some time ago. Back then, I had a Stone Armor Brute that I like for its survivability, but I remember it was very vulnerable to psionic damage. The Going Rogue expansion got me interested in playing again, but this time I want something with even more survivability than a Stone Armor melee. I would be posting this in the official CoH forums, but my account is not active yet and it seems like that is stopping me from logging in there.
I looked through the power sets and decided I definitely want to play a Tanker for their increased defense and taunting over Brutes. I feel like I will contribute better to the team that way. The other thing that I considered was psionic defense and resistance. Stone Armor could get soft-capped psi defense, but had almost no resistance. Willpower could get a little bit of both, but not enough to be very effective. Dark Armor had the most of both, and it had a lot of other resistances and defense.
I realize Dark Armor has a few weaknesses. First, the lack of knockback protection can be taken care of with a couple IOs and Acrobatics. The lack of energy resistance isn't as much of a vulnerability as some would make it seem like. At around 30% before IOs, it is better than Willpower's energy resistance. IOs could boost it up a decent amount. The overall defenses and resistances are not capped, but grouping with almost any buffer can cap defense or resistance for everything except psionic. For example, Thermal or Sonic can give out 20-30% resistance buffs, putting you close to the cap for energy resistance. Force Field can send you over the soft-caps for defense.
My conclusion was that Dark Armor's psionic defense and resistance makes it the only tanker who can theoretically have capped mitigation against anything. It may take a buffer or two, but no other armor set can reach capped mitigations against psionic, even with buffs.