In the scaled version you don't really need a tank, (AoE) dps is king there, and having a good cappy in the group is a real benefit. I can tank all three bosses (and whatever adds remain) on my champ in full dps gear+fervour without kiting if there is a good cappy in the group, so survivability really shouldn't be an issue.
Only tried it once on guard yet, but that run failed because the char was pretty fresh at 85, had very low ICPR and a rather bad group-setup (think it was PUG with mini and hunter or burg), so I ran out of power relatively fast. With higher ICPR and better gear now even that group should work. OTOH, if you can get a good cappy+champ in your group, might be easier to go OP and let the champ tank instead of "fighting" over aggro.
Used to play: 85 Champ / Captain / Runekeeper / Guardian, Guild Master of everything but cooking.
Playing now: Hellcat / King Tiger / GW Panther / IS / KV-5 / M4 Sherman and more