Shadows actually have weaker mitigation for Force/Tech attacks than Guardians and Vanguards, assuming they aren't Internal or Elemental damage. Only then do Shadows get a leg up. I should have clarified I meant Kinetic/Energy coming from Force/Tech attacks. This means the attack can't be shielded or defended (one of the Shadow tanks strengths) but is affected by all of your damage reduction including armor (Shadow tank weakness).
If you want to get purely technical, this only applies to *consistent* K/E damage from F/T attacks. Resilience actually allows a Shadow tank to ignore all F/T attacks for 5 seconds every 60 seconds, at worst (like when you're tanking Stormcaller and don't have any attacks to dodge/parry/block to reduce your Resilience CD with). If it's bursty damage, a Shadow is going to be the best tank you can have. It's only when it's consistent (Stormcaller, Kephess the Undying, Soa, Jarg, Zorn) that Shadows suffer (and it's not as bad as most people think because self-healing applies to *all* types of damage).