DK Tanks do benefit from melee totems.
DK Tanks do benefit from spell power totems.
DK Tanks can provide 20% melee haste (windfury is 16%) to party/raid (this is a talent, 26pts Frost)
DK Tanks can provide 155 str/agil to party/raid @ lvl 75, where Srength of Earth totem matches it at lvl 80 (this is a spell all specs get I believe)

My secondary toon is an enhantment shaman and yes, I easily dual box it currently with a paladin. I'd likely swap my totems around though.. right now it's usually Windfury/Flametongue/Strength/Mana to Wrath/Flametongue/Strength or Stoneskin/Health. Yeah, i'm a bit crazy running around with two melee types, but that's mainly for leveling and it's not as hard as you may think when it's only 2 toons. Once dual-spec comes out, I'll likely have a restro spec setup for the shaman so I can just nab some dps friends for some instance running. Then, when raiding, just run with my DK.

Worst case, I have my paladin I leveled up with the shaman as a backup.