Yes, I tanked the imps and Kil'rek while Gnostic tanked Illhoof. Here's how.
* Blessing of Sanctuary (80 dmg absorbed)
* Earthen Elixir (20 damage absorbed)
* Fire Protection Aura
* Fire resist gear (I had the entire Flamebane set for a net of 216 with my aura - any more is probably overkill)
* On the pull, cast Exorcism to grab Kil'rek.
* Cast Judgement of Wisdom on Illhoof, melee him throughout the fight to maintain it.
* Seal of Wisdom (again, to keep mana up).
* When the imps spawn, pop Consecration so it covers both portals.
* Continue to cast Consecration every time the cooldown is up. This may require you to move to ensure that you fully cover the portals.
That's basically it. Additional notes:
* You don't need to melee Kil'rek at all to hold his aggro. You don't even need to focus fire him with this strat - all DPS can go to Illhoof.
* Holy Shield is optional - you don't need it to hold Kil'rek and he can't deal crushing blows (level 70).
* Any additional mana not required to maintain Consecration can go to help DPS on Illhoof.
* Between Judgement/Seal of Wisdom and healing received, you should remain at nearly full mana throughout the fight.
* Do not
move to DPS the Demon Chains. You can't afford to let any imps get loose.
* If you get sacrificed, or take Amplify Flames, cast/cancel Divine Shield to clear it without losing aggro.
* I was taking 20-60 damage per Firebolt from the imps. We didn't use Dampen Magic, but it would probably have reduced those to zero. I'd like to try it next run.
Heck, I could probably have tanked Illhoof too, with enough heals. I was taking so many hits that Redoubt and Reckoning were up 100% of the fight.